Johann Berthelsen was born in Copenhagen in 1883, the 7th of seven children, to Conrad and Dorothea Karen Berthelsen. His parents were involved in artistic and professional circles. In 1890, his mother brought the children to America, settling in Manistee, Michigan, with her sister's family. They would eventually move to Manitowoc, Wisconsin, a city on the shore of Lake Michigan. As a teenager, Johann was actively involved in choirs and singing groups. And he always loved to draw and paint, and while he was too impatient to take well to schoolwork, and never went beyond the 5th grade.

Although he worked in several trades, Johann's mind and heart were always with the arts. As his voice matured, he also always wanted to be an actor, and at the age of 18 moved to Chicago where he reconnected with an old friend who was studying voice at the Chicago Musical College. He was awarded the school's Gold Medal on two occasions, and after graduation, he earned a job as the lead baritone with the newly formed Standard Opera Company which was owned by the Schuberts. For the next five years, Johann Berthelsen enjoyed a rich and varied career, touring the U.S. and Canada in operas, concerts, Gilbert & Sullivan, and operettas.

Despite considerable success, the grueling pace of life on the road was difficult, and in 1910 he joined the voice faculty at Chicago Musical College. So he eventually had more time to pursue other personal interests, especially painting. He became friends with the artist, Svend Svendsen, a noted landscape painter whose snow scenes especially intrigued Berthelsen, which became a major influence in his choice of mood and treatment of light and shadow. In 1913, at the age of 30, he became the youngest-ever head of the voice department at the Indianapolis Conservatory of Music.

In Indianapolis, he began a friendship with the painter, Wayman Adams. A native of Muncie, Indiana, Adams had studied with William Merritt Chase and Robert Henri in Spain and Italy and had already established a reputation as a portraitist. Adams and Berthelsen were to remain best friends for the remainder of their lives. Adams would paint many significant portraits of Berthelsen including a life-sized image of his friend preparing to go on stage.

In 1920, seeking to advance their careers, Berthelsen and Adams moved to New York, where both achieved rapid success. From 1920 through the late '50s, Wayman Adams painted some of his best-known works. Johann Berthelsen established a private school of singing instruction at the Rodin Studios and attracted a distinguished following, but in 1929, the heady prosperity of the Roaring '20s dissolved in the Stock Market crash, and the arts were among the hardest hit sectors.

With many Broadway theaters shuttered and the Metropolitan Opera cutting salaries, Johann's pupils disappeared. With the little money left, he purchased art supplies and canvases and began to refine his technique in oil painting. He painted quickly and prolifically, bringing his work to some of the leading galleries. Of the many subjects he painted, the one that he would become most identified with was the city itself. The New York snow scenes burst with movement; cars, trucks, taxis, and people seem to rejoice in the snow that turns the city into a wonderland. Though he was exclusively self-taught he owned his craft and technique.

As his paintings become more popular, his reputation increased. By 1940, his reputation had grown to the point where he was asked to join The Lecture Bureau of the Columbia Broadcasting System. In 1942 the family moved to rural New Milford, Connecticut, where Berthelsen painted many views of the surroundings.

With the end of the Second World War, the Depression finally ceased and in the first blush of post-war prosperity, the public again had the time and money to devote to the arts. As more prominent personalities began to collect his work, 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. The 1960s proved to be an especially satisfying time for Johann and his family since the financial pressures lessened and his paintings started commanding better prices. In 1971 he was hit by a car, which led to a decline in health and ultimately his death the following year 1972.