In 1870 at the age of 19 he completed his studies at the Royal Danish Academy of Art (Det Kongelige Danske Kunstakademi).
His official debut as a painter was in 1871 at Charlottenborg Palace with a portrait of a friend, painter Frans Schwartz. He exhibits regularly at Charlottenborg throughout his lifetime.
In 1874 Heinrich Hirschsprung buys his first painting from Krøyer, establishing a long-standing patronage. Hirschsprung's collection of art forms the basis of the Hirschsprung Museum in Copenhagen. Between 1877-1881, Krøyer travelled extensively in Europe, meeting artists, studying art, and devloping his skills and outlook. He stays in Paris and studies under Léon Bonnats, and undoubtably comes under the influence of contemporary impressionists-- Claude Monet, Alfred Sisley, Edgar Degas, Pierre-Auguste Renoir and Edouard Manet.
He continues travelling extensively throughout his life, constantly drawing inspiration from foreign artists and cultures. Hirschsprung provided financial support during the early travels, and Krøyer continued exhibiting in Denmark throughout this period.
In 1882 returning to Denmark he spent June-October at Skagen, painting themes from the local life, as well as depictions of the other artistic and influential people who lived in and visited Skagen during those times. He would continue to be associated with Skagen, and the developing art and literary scene at Skagen over many years. Others who would be associated with the community of artists in Skagen were writers Holger Drachmann, Georg Brandes, and Henrik Pontoppidan, artists Michael Ancher and Anna Ancher.
He married Marie Martha Mathilde Triepcke on July 23. 1889. Marie Krøyer also became a painter associated with the Skagen community. They separated in 1905.
Krøyer's best known and most well loved work is entitled "Summer evening on Skagen's south beach with Anna Ancher and Marie Krøyer" (Sommeraften ved Skagen Sønderstrand med Anna Ancher og Marie Krøyer), 1893. He painted many beach scenes featuring both the recreation life on the beach (bathers, strollers), as well as local fishermen.
A second work that is also well loved is entitled "Saint John's evening bonfire on Skagen's beach" (Sankthansbål på Skagen strand), 1903. This large-scale work features a great crowd of the artistic and influential Skagen community gathered around a large bonfire on the beach on Saint John's Eve (Midsummer Eve).
Both of these works are in the permanent collection of the Skagens Museum.
Krøyer died in 1909 at 58 years of age after several years of declining health.