[3] He set the inaugural world record in the pentathlon in Gothenburg in 1911 with a score of 5516 points.

The following year, he finished second in the decathlon at the 1912 Summer Olympics in Stockholm, 688 points behind Jim Thorpe.

Wieslander was declared the winner of the 1912 Olympics event and awarded the gold medal, which he refused to accept.

[4] In 1982, Thorpe was reinstated by the IOC with Hugo Wieslander as joint winners of the 1912 Olympic decathlon.

[7] In 1913, he passed the state surveying exam and became employed by the Swedish cartography agency (sv:Rikets allmänna kartverk).