|Olympic medal record|
|1908 London||Medley relay|
|1912 Stockholm||400 metres|
|1908 London||800 metres|
He won the bronze medal in the men's 800 metres race at the 1908 Summer Olympics in London with a time of 1:55.2, which was .8 seconds faster than the previous Olympic record but 3 seconds slower than the time of Mel Sheppard, the winner of the race. His semifinal time had been 1:58.0.
Braun was also a member of the silver medal German medley relay team. He ran the final 800 metres of the 1600 metre race, following Arthur Hoffmann, Hans Eicke, and Otto Trieloff. The team had an easy time defeating the Dutch squad in the first round, finishing in a time of 3:43.2. The final was a more difficult race, however, and the Germans never had a chance of catching the Americans. The first three runners found themselves in third place, and Braun began his leg five yards behind the Hungarian runner. He was able to catch up and pass Ödön Bodor, however, giving the Germans a second-place victory of a tenth of a second at 3:32.4.
Braun also ran in the 1500 metres. He placed third in his first round (semifinal) heat with a time of 4:18.2 and did not advance to the final.
- "Hanns Braun". Sports Reference. Archived from the original on 17 April 2020. Retrieved 3 August 2015.
- "Olympians Who Were Killed or Missing in Action or Died as a Result of War". Sports Reference. Archived from the original on 17 April 2020. Retrieved 3 August 2015.