Born in 1868 (Meiji 1) in Mito, Hitachi Province (today Mito, Ibaraki), as the eldest son of the former Mito-domain samurai Sakai Sutehiko; his given name was Hidemaro, later changing to the surname Yokoyama. In 1889 he entered the Tokyo School of Fine Arts (today Tokyo University of the Arts) as a first-year student in the Japanese painting department, studying under Okakura Tenshin, Hashimoto Gaho, and Kawabata Gyokusho. He graduated head of his class in 1893 and became assistant professor at his alma mater (1896). In 1898, in solidarity with Okakura Tenshin in his exclusion from the Tokyo School of Fine Arts (the Bisei Soudou), he resigned and, together with Hishida Shunso, Shimomura Kanzan, and Saigo Kogetsu, joined the 'Nihon Bijutsuin' (Japan Art Institute) Tenshin newly founded in Yanaka. Together with Shunso he there originated the innovative 'morotai' (vague style) of expressing form by color alone with restrained line, but it was at first roundly criticized as 'unclear.' In 1903 he traveled to India and the Bay of Bengal, and in 1904 to New York, Boston, London, and Paris, seeking a fusion of Eastern spirituality and Western technique. After Tenshin's death in 1913, in 1914 he and Kanzan revived the Japan Art Institute (the revived Inten exhibitions) and became the central figure of modern Japanese painting circles. The 'Seisei Ruten' of 1923 (total length 40.7 meters), depicting the cycle in which a drop of water becomes cloud, river, and sea, is a monument of ink painting (Important Cultural Property). In 1937 he received the first Order of Culture. He died at his Ueno Ikenohata home in Tokyo on February 26, 1958, at 89.

He combined absolute veneration and loyalty to Okakura Tenshin with deep grounding in tradition and an unceasing pursuit of new expression. The art name 'Taikan' was given by Tenshin, and he devoted his life to embodying Tenshin's ideals. He painted Mount Fuji about 1,500 times in his life, viewing it as the symbol of Japanese spirituality. Known as a heavy drinker, he openly said 'I paint drunk,' and there are many anecdotes of his refusing to take up the brush without sake. He never married and led a life devoted entirely to painting.

Establisher of modern Japanese painting and its greatest star. He inherited Okakura Tenshin's ideals and, through prewar and postwar alike, was the central figure of Japanese painting circles. Representative works such as 'Seisei Ruten' (National Museum of Modern Art, Tokyo), 'Qu Yuan,' 'Muga' (Selflessness), 'Maples,' and 'Cherry Blossoms at Night' include many National Treasures and Important Cultural Properties. He received the first Order of Culture in 1937, and after the war was entrusted three times — in 1937, 1955, and 1958 — with the fusuma paintings of the Imperial Palace. The Yokoyama Taikan Memorial Museums in his native Mito, Ibaraki, and at Ueno Ikenohata hold and display about 2,000 of his works. Famous for his Mount Fuji paintings, the image 'Japanese painting equals Taikan' continued long after the war.