The son of a decorative painter, Leonard Ochtman settled with his family in Albany, New York, in 1866. By age 16, he was working as an engineer, a job he held for nearly ten years. In his free time, Ochtman painted the scenery surrounding Albany. Shortly after a trip to Europe in 1885, he moved to New York, where he shared a studio with Charles W. Eaton. At this time, he spent one season at the Art Students League. The year 1891 marked his election to the Society of American Artists and his marriage to painter Mina Fonda. The couple settled in Greenwich, Connecticut, where Ochtman soon gave classes. Their Connecticut home, Grayledge, was built in 1896, and he was henceforth associated with the artists colony at Cos Cob.
Between 1902 and 1904, Ochtman received a series of four prestigious awards at the annual exhibitions of the National Academy of Design and the Society of American Artists. His plein-air Connecticut landscapes became regular additions to Academy Annuals until his death. Ochtman was also very active in the Greenwich Society of Artists, serving as its president from 1916 to 1932. Seven years before his death, he left Connecticut for a European trip. His daughter, Dorothy, was also an artist.