Munjal was born in 1923 at Kamalia, district Toba Tek Singh in unpartitioned Punjab, British India. Kamalia is now in Pakistan. He was from a simple middle-class Arora/Khatri family. After completing his formal education, he worked at the Army Ordnance Factory, before moving his base to India after partition.
In 1954, Hero Cycles moved up the value chain by making a shift from supplying to Manufacturing handlebars, front forks and chains. In 1956, the Punjab Government issued tender notices for twelve new industrial licenses to make bicycles in Ludhiana. Munjal and his brothers participated in the bid and won the contract. Hero Cycles was registered as a large-scale industrial unit. with capital partly financed by the Government of Punjab.
In 1961, Rockman Cycles Industries was established to manufacture bicycle chains and hubs. Under Munjal's leadership, Hero Cycles was the first company to export bicycles on such a large scale. In 1975, the company had become the largest bicycle manufacturer in India. By 1986, Hero Cycles entered the Guinness Book of Records as the largest manufacturers of bicycles in the world.
Before entering into a joint venture with the Honda Motors, Munjal started a Majestic Auto and started Manufacturing of the Hero Majestic Moped. To manufacture motor cycles in 1984, the Hero Group started a joint venture with Hero Honda and established a plant at Dharuhera, Haryana. The Hero Group became so large that by 2002 it had sold 8.6 million bicycles, and was producing 16,000 motorcycles a day.
After the Hero Honda Motors joint venture broke up in August 2011, Hero's board of Directors agreed to pay royalties to Honda to continue to produce the Hero Honda until 2013, due to the popularity and ubiquity of the Hero Honda brand in the Asia Pacific region as Hero Honda Brand was trusted among the best in the Product reliability and customer satisfaction.
In the first week of August 2013, the company recorded a benchmark never before reached by an Indian two-wheel vehicle industry manufacturer, by producing 50 million bikes.
Brijmohan was married to Santosh and had five children: Raman Kant (deceased), Suman Kant, Pawan Kant, Sunil Kant and a daughter, Geeta Anand. He died on 1 November 2015 in South Delhi after a short illness.