The first participation in a national high jump competition was made by Maksim Nedassekau on June 7, 2014. The following year he jumped the two meters for the first time. In 2016 he represented Belarus at the U20 World Championships in Bydgoszcz , where he finished eighth with 2.18 m. The following year he won the high jump competition at the U20 European Championships in Grosseto with a jump of 2.33 m, which was a new personal best and a championship record. In 2018 he qualified for the World Indoor Championships in Birmingham , where he jumped sixth with 2.20 m. At the European Championships in Berlin he equalized his best performance and won the silver medal behind the German Mateusz Przybylko . The following year he was eliminated from the qualification at the European Indoor Championships in Glasgow with 2.21 m and won the gold medal at the U23 European Championships in Gävle with a height of 2.29 m. He had already won the European Games in Minsk with 2.27 m. He also qualified for the World Championships in Doha , where he finished fourth with 2.33 m in the final , before he came eighth at the Military World Games in Wuhan with 2.05 m.
In 2017 Nedassekau became the Belarusian outdoor champion and in 2018 indoor.