Although many artists refused to accept an African-American apprentice, in 1879 Tanner enrolled at the Pennsylvania Academy of the Fine Arts in Philadelphia, becoming the only black student. His decision to attend the school came at an exciting time in the history of artistic institutional training. Art academies had long relied on tired notions of study devoted almost entirely to plaster cast studies and anatomy lectures. This changed drastically with the addition of Thomas Eakins as “Professor of Drawing and Painting” to the Pennsylvania Academy. Eakins encouraged new methods, such as study from live models, direct discussion of anatomy in male and female classes, and dissections of cadavers to further familiarity and understanding of the human body. Eakins’s progressive views and ability to excite and inspire his students would have a profound effect on Tanner. The young artist proved to be one of Eakins’ favorite students; two decades after Tanner left the Academy, Eakins painted his portrait, making him one of a handful of students to be so honored.

In 1891 he traveled to Paris, France, to study at the Académie Julian. He also joined the American Art Students Club. Paris was a welcome escape for Tanner; within French art circles the issue of race mattered little. Tanner acclimated quickly to Parisian life. Except for occasional brief returns home, he spent the rest of his life there.

In 1893 on a short return visit to the United States, Tanner painted his most famous work, The Banjo Lesson, while in Philadelphia. The painting shows an elderly black man teaching a boy, assumed to be his grandson, how to play the banjo. This deceptively simple-looking work explores several important themes. Blacks had long been stereotyped as entertainers in American culture, and the image of a black man playing the banjo appears throughout American art of the late 19th century. Thomas Worth, Willy Miller, Walter M. Dunk, Eastman Johnson, and Tanner’s teacher Thomas Eakins had tackled the subject in their artwork.

He studied under renowned artists such as Jean Joseph Benjamin Constant and Jean-Paul Laurens. With their guidance, Tanner began to establish a reputation. He settled at the Étaples art colony in Normandy. Earlier Tanner had painted marine scenes of man’s struggle with the sea, but by 1895 he was creating mostly religious works. Tanner’s shift to painting biblical scenes occurred as he was experiencing a spiritual struggle, evidenced by a letter he wrote to his parents on Christmas 1896 in which he stated, “I have made up my mind to serve Him [God] more faithfully.” A transitional work from this period is the recently rediscovered painting of a fishing boat tossed on the waves, which is held by the Smithsonian American Art Museum.

In 1899 he married Jessie Olsson, a Swedish-American opera singer. A contemporary, Virginia Walker Course, described their relationship as one of equal talents, but racist attitudes insisted the relationship was unequal: “Fan, did you ever hear of a miss [sic] Olsson of Portland? She has a beautiful voice I believe and came to Paris to cultivate it and she has married a darkey artist … He is an awefully [sic] talented man but he is black. … She seems like a well educated girl and really very nice but it makes me sick to see a cultivated woman marry a man like that. I don’t know his work but he is very talented they say.” Jessie Tanner died in 1925, twelve years before her husband, and he grieved her deeply through the Twenties. He sold the family home in Les Charmes where they had been so happy together. They are buried next to each other in Sceaux, Hauts-de-Seine. They had a son Jesse, who survived Tanner at his death.

Tanner’s work was influential during his career; he has been called “the greatest African American painter to date.” The early paintings of William Edouard Scott, who studied with Tanner in France, show the influence of Tanner’s technique. In addition, some of Norman Rockwell’s illustrations deal with the same themes and compositions that Tanner pursued. Rockwell’s proposed cover of the Literary Digest in 1922, for example, shows an older black man playing the banjo for his grandson. The light sources are nearly identical to those in Tanner’s Banjo Lesson. A fireplace illuminates the right side of the picture, while natural light enters from the left. Both use similar objects as well such as the clothing, chair, crumpled hat on the floor. Some other major artists Tanner mentored include William A. Harper and Hale Woodruff.

In his adopted home of France, he was given one of its highest honors in 1923, when he was appointed Chevalier of the Legion of Honor, the highest national order of merit, and considered this “citation by the French government to be the greatest honor of his illustrious career.”

During World War I, Tanner worked for the Red Cross Public Information Department, during which time he also painted images from the front lines of the war. His works featuring African-American troops were rare during the war. In 1923 the French state made him a knight of the Legion of Honour for his work as an artist.

Tanner died peacefully at his home in Paris, France, on May 25, 1937. He is buried at Sceaux Cemetery in Sceaux, Hauts-de-Seine, which is a suburb of Paris.