In 1835, Konstantin accompanied his parents to Germany and from age eight onwards was taught to keep a diary. When he was just eight years old, he was given a small yacht, which he would sail between Petergof and Kronstadt, spending his days at sea and returning home at night. In 1836, accompanied by Litke, he embarked on a lengthy sailing expedition and finally he was given command of the Russian frigate Hercules under Litke's direction. During his training Konstantin was treated like all other naval cadets, even to the point of his title of Grand Duke being dispensed with. He was placed on watch duty at midnight as well as in rain and storms. At the age of sixteen, Konstantin was promoted to the rank of captain and served as commander of the frigate Ulyses, visiting various ports along the Gulf of Finland and embarking on a southern tour that included the Mediterranean.
In 1846 Konstantin's sister, Grand Duchess Olga, married Crown Prince Charles of Württemberg. He went with her to Stuttgart then he continued to Altenburg to be introduced to Princess Alexandra of Saxe-Altenburg. His parents had arranged the meeting thinking that Alexandra might make a good match for Konstantin. Alexandra was strikingly beautiful, tall and slim and Konstantin was immediately eager to marry her. "I don't know what is happening to me. It is as if I am a completely new person. Just one thought moves me, just one image fills my eyes: forever and only she, my angel, my universe. I really do think I’m in love. However, what can it mean? I've only known her a few hours and I'm already up to my ears in Passion".
Konstantin had five illegitimate children with his mistress Anna Kuznetsova (1847–1922); they bore the last name Knyazev:
In 1849, as a young officer, Konstantin took part in a campaign assisting the Habsburgs to put down a revolution in Hungary. It was his first real taste of military conflict. He took part in three dangerous clashes, coming under enemy fire. For his bravery he received the Cross of St. George. During this campaign, he wrote to his Father who maintained they were the best reports he received. A year later, Konstantin was appointed a member of the State Council.
In 1853, Konstantin's Father Tsar Nicholas I made him General-Admiral of the Imperial Navy and head of the Department of the Imperial navy. In this position, he was in charge of reforming a navy that had largely remained unchanged since the time of Peter the Great. It fell upon Konstantin to not only preside over an archaic fleet but also to see it through the disaster of the Crimean War. In the midst of the conflict, his Father died and Konstantin advised his brother to search for peace in a war already lost. In early 1856, he accompanied his brother Alexander II to the Crimea to view first-hand the devastation of the War. These early military experiences gave Konstantin a loathing of army life and the futility of war. From then on, he was a man of peace, despite his keen interest in the navy, and in political terms a progressive. There was a close working relationship between the two brothers, which was responsible for many reforms. Konstantin was also sent on a diplomatic mission to Napoleon III.
The most important reform of all was the emancipation of the serfs, a policy that was unpopular with large sections of the nobility. When the committee appointed to bring it about dug in their heels and made difficulties, Alexander II asked Konstantin to join the committee in September 1857. Where the Tsar was unsure of himself, his younger brother was more forceful, quick tempered, and cared not what others might think of him.
In 1858, a central group for emancipation, which included only the more progressive members, Konstantin, Lanskoy, Yakov Rostovtsev, Nikolay Milyutin, and their allies, replaced the original committee. Even then, progress was still slow, particularly as several members objected to the Grand Duke's brusque manner.
At the end of the 1860s, Konstantin embarked on an affair, having an illegitimate daughter, Marie Condousso. In the 1880s, Marie was sent to Greece, later serving as lady in waiting to her half sister, Queen Olga. Marie eventually married a Greek banker. Soon after the birth of Marie, Konstantin began a new liaison. Around 1868, Konstantin began to pursue a young Dancer from the St. Petersburg Conservatoire. Anna Vasilyevna Kuznetsova was a talented ballerina and a mime. She was the illegitimate daughter of ballerina Tatyana Markyanovna Kuznetsova and actor Vasily Andreyevich Karatygin. Anna was twenty years younger than Konstantin and initially she resisted his advances, but in 1873 she gave birth to their first child. Four more would follow.
Although his brother never ceased to support him, after twelve stormy months Konstantin decided he had had enough of "the ignoble nobility". Frustrated and disheartened, he departed for a relaxing cruise abroad. He returned to his post almost a year later, refreshed by his absence. The brothers' joint determination for results eventually paid off. A general plan of procedure was soon produced and after almost five years, the emancipation finally became law in 1861. Alexander II publicly thanked Konstantin for his contribution.
In July 1862, Konstantin's wife gave birth to the couple's sixth and last child in Warsaw. As a compliment to the Poles, they decided to give their son a Polish name, Vacslav, but the Russians insisted that the true Russified form, Vyacheslav, should be used, a compromise which pleased neither nation. Alexander II's second son, Grand Duke Alexander, was sent to Warsaw to stand as a godfather to the child. A large, clumsy youth of seventeen, the Future Alexander III spilt a decanter of red wine at the dinner table. Konstantin, with his abrupt manners, scolded his clumsy nephew, remarking "See what a pig they have sent us from St. Petersburg". The Future Alexander III would never forget this insult and for the rest of his life he bore a grudge against his uncle.
Back in St. Petersburg, Konstantin devoted all his attention to the navy. He spent seven years reforming the Naval Department, altering laws and reorganizing training of recruits, and successfully managed to transform the previous, often-grim conditions on board most vessels to meet modern standards and expectations. Corporal punishment was abolished in 1863 and the traditional system of naval recruitment was drastically altered.
Since 1865, Konstantin had been pushing for a constitution in Russia. As President of the Council of State, he helped to prepare the proposal for a limited elective assembly which Alexander II was due to approve on the very day he was assassinated. For Konstantin and his fellow reformers, hopes ended within months of the new Emperor's ascension to the throne. Alexander III destroyed the document and as he never had liked his uncle Konstantin, whom he regarded a 'liberal powerhouse', requested his uncle's resignation. Konstantin refused to resign, saying that his Father "had directed me to serve both my deceased brother, and his successors. In my capacity as chairman of the State Council, and as Admiral-General of the Imperial navy, I plan to serve Your Majesty with just as much faith and Energy. By doing so, I will fulfill my beloved father's last wishes". This was not the answer Alexander III had anticipated and the second time he presented his uncle not with a suggestion but with an order. After sixteen years as chairman of the Council of ministers, Konstantin was stripped of the office and was replaced by his brother, the more pliable Grand Duke Mikhail Nikolayevich; Alexander III also took away Konstantin's position as head of the Naval Department, handing it over to his own brother, Grand Duke Alexei Alexandrovich. Konstantin was no longer welcome at court.
In 1867, Konstantin's eldest daughter, Olga, married King George I of Greece. She was only sixteen, and Konstantin was initially reluctant to let her marry so young. In July 1868 Olga's first child was born and was named Konstantin after his grandfather. The start of his daughter's family coincided with the breaking up of Konstantin's marriage.
In 1874, scandal erupted when it was discovered that Konstantin's eldest son, Grand Duke Nikolay Konstantinovich, who had lived a dissipated life and had revolutionary ideas, had stolen three valuable diamonds from an icon in the bedroom of Alexandra Iosifovna in complicity with his mistress, an American courtesan. His twenty-four-year-old son was found guilty, declared insane, and banished for life to Central Asia. Konstantin suffered another bitter blow when in 1879, his youngest legitimate son, Vyacheslav, died unexpectedly from a brain hemorrhage.
The dismissal fell heavily on the still vibrant, energetic Konstantin, leaving him adrift without any proper role. He was an enthusiastic chess player and his chess problems were published in international journals, but that was not a substitute for the position he once had at the center of affairs. He spent increasingly more time with his second family, further humiliating his legitimate wife. With nothing left to do, Konstantin retired to Pavlovsk, spending most of his time abroad or on his Crimean estate of Oreanda. In August 1881 a fire completely destroyed Oreanda. The palace was never rebuilt and Konstantin lived from then on in a wooden pavilion. Tragedy struck him again while living there. In April 1885, his two surviving illegitimate sons died days apart of scarlet fever. Of the five children Constantin had had with Kousnetzova, only the two daughters, Marina and Anna, thrived; Konstantin showered them with affection. He was also particularly close to his eldest daughter Olga whom he visited in Greece in 1883. His grandson Prince Christopher of Greece remembered him for his sharp and loud voice, which Konstantin enjoyed using, usually for new servants and preferably in the presence of guests. Without any reason he would glare at the new servant and then scream the servant's name. Some were used to the trick and remained calm, while others dropped the dishes in terror, which amused him.
In 1886, Konstantin was furious when Alexander III restricted the title of Grand Duke to only children and grandchildren of Emperors, as this meant that Konstantin's grandchildren would merely be princes, but there was little he could do. He had been shunned from society and Alexander III only called his uncle to court for the wedding of Konstantin's eldest granddaughter, Alexandra of Greece to his nephew Grand Duke Paul.
At the beginning of August 1889, Konstantin suffered a severe stroke that left his legs paralyzed and him unable to speak. The loss of his health struck the once vibrant Konstantin particularly hard. As an invalid, he depended from then on on the care of adjutants while confined in a bath chair. Konstantin was cared for by his wife, who gained a sort of revenge for his unfaithfulness and past humiliations. Alexandra Iosifovna did not expel Anna Kuznetsova and her children from the nearby house that Konstantin had provided for them, but she made sure that Konstantin's attendants never took him there.
Konstantin died at Pavlovsk on 25 January 1892. Before he died his wife invited his mistress and their two daughters to see him for a last time.
Konstantin bought his second family a large, comfortable dacha on his estate at Pavlovsk, in fact lodging his mistress and their illegitimate children in close proximity to his estranged wife who he now referred to as his "government–issue wife". Once more Konstantin gave ammunition to his enemies and society sided in the scandal with his suffering wife, who tried to bear his infidelity with dignity.
Although he was only forty, Konstantin's struggles and travails of the previous decade—naval and judiciary reforms, the freeing of the serfs—had prematurely aged him. As Alexander II turned away from the reforms that had marked his first decade on the throne, Konstantin's influence began to wane and he began to focus more in his personal life. After twenty years of marriage he had drifted away from his wife, their divergent political views and interests slowly tearing away the foundations of their marriage. Alexandra Iosifovna was as conservative as her husband was liberal, self-absorbed with her own beauty and her mysticism. Soon, Konstantin turned elsewhere for comfort.