With more than 100 appearances to his name, Nicholson brings depth to the wing at Minnesota, where he can play on either the right or the left. He also has international experience with Scotland at the U-21 level.
"We are really pleased to have added a player with the skill set of Sam (Nicholson)," Minnesota head coach Adrian Heath said in a press release.
"He's a player who can cut inside from either side of the pitch. He's got two really good feet and he's got some goals in him, he can beat his man. It's not very often that you get the opportunity to bring in a player from Europe, who looks at MLS as a step up. We are delighted to have him and we think he will be a great addition to our squad."
Nicholson, for his part, said he is "absolutely delighted" to sign with the Loons.
"It was an easy decision after speaking with the coaching staff, everyone made me feel comfortable and at home straight away," Nicholson said. "It's a great club and I am excited for the new challenge ahead in MLS and I cannot wait to play in front of all the amazing fans."