Johann Henrik Carl Berthelsen was born in Copenhagen, Denmark, the youngest of seven sons born to Conrad and Dorothea Karen Berthelsen. His father was a tenor with the Royal Opera and his mother, a nurse. Following the divorce of the parents, in 1890 his mother brought the children to America where they settled in Manitowoc, Wisconsin.
Johann developed an early interest in singing, acting, drawing, and painting. He dropped out of school after the fifth grade and worked at various jobs. Planning to pursue a career in theater, at age 18 he moved to Chicago, and eventually enrolled at the Chicago Musical College with a full scholarship.
Following his graduation in 1905, he toured the United States and Canada, performing in operas, Gilbert & Sullivan operettas, and concerts until 1910, when he began teaching voice at the Chicago Musical College. In his spare time he pursued painting, with encouragement and some instruction from the Norwegian-American Impressionist painter Svend Svendsen.
In 1913, Berthelsen moved to Indianapolis to become the head of the voice department at Indianapolis Conservatory of Music. He formed a lifelong friendship with painter Wayman Adams. Adams would paint many portraits of Berthelsen, including a life-sized image of his friend about to go on stage for a concert. Adams is credited by some as having provided painting instruction to Berthelsen.
In 1920, Adams and Berthelsen moved to New York City to further their careers. Berthelsen opened a private school of voice in the Rodin Studios building. One of his pupils was a singer, dancer and entertainer named Helenya Kaschewski, whom he married on March 15, 1928. They had three children—a daughter, Karen, and two sons, John and Lee. He continued to pursue art, and in 1925 he was elected to the American Watercolor Society. He also mastered the pastel medium during the 1920s.
With the Great Depression Berthelsen lost his voice students, and the family had to sell many of their possessions and move to an ever-smaller series of apartments. A fellow artist suggested painting in oils, which he began to do, and he had gradually increasing success in selling his canvases. In the mid-1930s he was also involved in several New Deal art projects. He joined the Salmagundi Club in 1935 and remained a member until his death.
In 1942 the family moved to rural New Milford, Connecticut, where Berthelsen painted many views of the surroundings. But his most popular canvases represented New York City scenes, particularly snow scenes. His works were collected by prominent figures including William Randolph Hearst, Richard E. Berlin, Frank Sinatra, Ethel Merman, and Dinah Shore.
In 1950 the family moved back to New York City, in part because of the high demand for his work and easy access to galleries. He exhibited his work at the Barbizon-Plaza Galleries, the Allan Rich Gallery, and the Jean Bohne Gallery, among others. He continued to paint well into his eighties, until his death in 1972.
Brooklyn Bridge, Oil on canvas, c. 1940s, 20 x 16 inches