He was born in Des Moines, Iowa and moved several times growing up due to his father's job as a football coach.

[3] He played mostly on special teams and as a reserve linebacker and as a true freshman, blocking a punt and returning the ball for a touchdown against Northwestern.

He was named honorable mention All-Big Ten again as a senior after making 80 tackles (six for loss), a sack, five passes broken up and two forced fumbles.

[4] Niemann signed with the Kansas City Chiefs as an undrafted free agent and made the final 53-man roster out of training camp.

[7][8] He made his NFL debut on September 9, 2018, in the season opener against the Los Angeles Chargers, playing on special teams.

[9] Niemann made his first career start on November 11 in the Chiefs 26–14 win over the Arizona Cardinals and led the team with 6 tackles.