After returning from Rome in 1719, he began painting in his topographical style. His first known signed and dated work is Architectural Capriccio (1723, Milan, in a private collection). Studying with the older Luca Carlevarijs, a well-regarded Painter of urban cityscapes, he rapidly became his master's equal.
In 1725, the Painter Alessandro Marchesini, who was also the buyer for the Lucchese art collector Stefano Conti, had inquired about buying two more 'views of Venice', when the agent urged him to consider instead the work of "Antonio Canale... it is like Carlevaris, but you can see the sun shining in it."
In the 1740s Canaletto's market was disrupted when the War of the Austrian Succession led to a reduction in the number of British visitors to Venice. Smith also arranged for the publication of a series of etchings of "capricci" (or architectural phantasies) (capriccio Italian for fancy) in his vedute ideale, but the returns were not high enough, and in 1746 Canaletto moved to London, to be closer to his market.
Many of his pictures were sold to Englishmen on their Grand Tour, often through the agency of the merchant Joseph Smith (who was later appointed British Consul in Venice in 1744). It was Smith who acted as an agent for Canaletto, first in requesting paintings of Venice from the Painter in the early 1720s and helping him to sell his paintings to other Englishmen.
Joseph Smith sold much of his collection to George III, creating the bulk of the large collection of works by Canaletto owned by the Royal Collection. in 1762, George III paid £20,000 for Consul Smith's collection of 50 paintings and 142 drawings. There are many examples of his work in other British collections, including several (19) at the Wallace Collection and a set of 24 in the dining room at Woburn Abbey. A large set of Canaletto works was also part of the collection of the Earls of Carlisle, however many were lost at the 1940 fire of Castle Howard and others were sold over the last century. Among those formerly at the Carlisle collection are "The Bacino di San Marco: looking East", now at the Museum of Fine Arts, Boston (sold in 1939) and the pair "Entrance to the Grand Canal from the Molo, Venice" and "The Square of Saint Mark's, Venice", now at the National Gallery of Art, Washington DC (sold in 1938). The last important venetian veduta at Castle Howard was by Bernardo Bellotto, "A View of the Grand Canal Looking South from the Palazzo Foscari", which was sold at Sotheby's in July 2015 for £2.6 million.
After his return to Venice, Canaletto was elected to the Venetian Academy in 1763 and appointed prior of the Collegio dei Pittori. He continued to paint until his death in 1768. In his later years he often worked from old sketches, but he sometimes produced surprising new compositions. He was willing to make subtle alternations to topography for artistic effect.
Canaletto's views always fetched high prices, and as early as the 18th century Catherine the Great and other European monarchs vied for his grandest paintings. The record price paid at auction for a Canaletto is £18.6 million for View of the Grand Canal from Palazzo Balbi to the Rialto, set at Sotheby's in London in July 2005.
Canaletto's early works remain his most coveted and, according to many authorities, his best. One of his early pieces is The Stonemason's Yard (c. 1725, the National Gallery, London) which depicts a humble working area of the city. It is regarded one of his finest works and was presented by Sir George Beaumont in 1823 and 1828.
His graphic print S. A. Giustina in Prà della Vale was found in the 2012 Nazi loot discovery.
Much of Canaletto's early artwork was painted "from nature", differing from the then customary practice of completing paintings in the studio. Some of his later works do revert to this custom, as suggested by the tendency for distant figures to be painted as blobs of colour – an effect possibly produced by using a camera obscura, which blurs farther-away objects – although research by art historians working for the Royal Collection in the United Kingdom has shown Canaletto almost never used a camera obscura.