Cohen, a 6-6, 180-pounder, will arrive on campus this summer and have four years of eligibility with the Golden Eagles.
"We are thankful to add Sandy to our class," Williams said. "The longer I do this, the more important it becomes to me, that the guys we bring into our program are humbled by the opportunity and really excited for the chance and haven't become spoiled by the process. Sandy is the perfect example of that.
"He has a very upbeat personality and it has been a joy throughout the process getting to know Sandy, his family, and coaches," Williams added. "We are excited to add to our roster another player from our state who represents who we are on and off the floor. He is a late bloomer in some respects, but because of his demeanor, he has leadership qualities he doesn't even realize yet. As his career unfolds, those will be incredibly important to us. He had a quick ascent nationally over the last six months and I believe he is just scratching the surface of what he will be."
A consensus top-100 prospect, Cohen is rated 84th in the ESPNU Top 100, 85th by Scout.com and 97th by Rivals.com.
Cohen averaged 16.6 points and 7.2 rebounds per game as a junior at Seymour High School under head coach Jon Murphy. He was a first team all-conference honoree and was tabbed honorable mention all-state by the Wisconsin Basketball Coaches Association.
Seymour won the league title in Cohen's freshman campaign in 2010-11 and advanced to the state tournament semifinals. The squad has made it to the sectional stage each of the last two seasons and Cohen is on pace to become the program's 10th 1,000-point scorer in school history.
He competes on the AAU circuit for Wisconsin Playground Elite under head coach Ike Wilson.
Marquette's 2014 recruiting class is currently ranked among the top-20 groups in the nation. ESPN.com ranks the commitments 15th, while Scout.com has them positioned 16th. MU has collected multiple nationally ranked classes since Williams took over the program in 2008.