Johannes Eriksen competed in three Olympic Games. He came close to winning a medal in 1908 (Middleweight) and 1912 (Middleweight B) reaching the quarterfinals and round 5, respectively. Finally, in 1920, he clinched the bronze medal in the light-heavyweight division. After losing to future gold medalist Claes Johanson in the quarterfinals, he advanced to the 2nd place final round. After an easy win over Jan Sint, he lost the bout for silver against Edil Rosenkvist. When his opponent in the fight for bronze, Eriksen’s compatriot Axel Tetens, withdrew, Eriksen was awarded the bronze medal.
Eriksen also had a long and successful career at national and local championships. He placed third in the middleweight at the 1909 Danish championships and won two championship titles for Copenhagen in 1919 and 1920. His last top placing came in 1925 as runner-up in the heavyweight of the Copenhagen championships.