He chose to attend college at Michigan State,[2] and averaged 6.7 points and 5.2 assists per game in 35 games as a freshman.[3] As a sophomore, he became a full-time starter, averaging 12.6 points and 6.9 assists per game for the Spartans, and earning third-team All-Big Ten Conference honors.[4]
Prior to the start of the 2019–20 season, Winston was unanimously named a preseason All-American by the Associated Press (AP), the only player so honored.[9] On December 29, Winston missed a game against Western Michigan with a bone bruise in his knee.[10] He scored a career-high 32 points along with nine assists in a 87–69 win over Michigan on January 5, 2020.[11] Winston passed Mateen Cleaves' Big Ten record of 816 assists on January 17, in a win against Wisconsin.[12] At the close of the regular season, Winston was named to the First Team All-Big Ten by the coaches and media.[13] Winston averaged 18.3 points and 5.9 assists per game as a senior.[14]
On August 19, 2021, Winston signed a second two-way contract with the Wizards.[16] He appeared in 7 games for the Wizards during the 2021-2022 regular season.[17]
Winston has two younger brothers, Zachary and Khy, who played basketball at Albion College. On November 9, 2019, Zachary Winston was killed after being struck by a train.[22]
^McCabe, Mick (March 21, 2016). "Cassius Winston named Michigan's Mr. Basketball". Detroit Free Press. Retrieved January 30, 2019.
^O’Donnell, Ricky (September 18, 2015). "4-star PG Cassius Winston commits to Michigan State, puts Tom Izzo on brink of his best recruiting class ever". SBNation.com. Retrieved January 30, 2019.
^Solari, Chris (June 13, 2017). "MSU's Cassius Winston plans summer packed with court time". Detroit Free Press. Retrieved January 30, 2019.
^Austin, Kyle (January 18, 2019). "Michigan State's Cassius Winston's recent play could make him a Big Ten Player of the Year contender". NCAA.com. Retrieved January 30, 2019.
^Austin, Kyle (October 10, 2018). "Preseason writers poll predicts Big 10 conference win for MSU, second for Michigan". MLive. Retrieved January 30, 2019.
^Sullivan, Crowley (January 10, 2019). "Wooden Award Midseason Top 25 - Is Cassius Properly Positioned?". USA Today. Retrieved January 30, 2019.
^Charboneau, Matt (March 11, 2019). "Michigan State's Cassius Winston named Big Ten Player of Year; Tillman top sixth man". The Detroit News. Retrieved April 1, 2019.
^"Michigan State knocks off Duke 68-67 to make Final Four". ESPN. Associated Press. March 31, 2019. Retrieved January 18, 2020.
^Marshall, John (October 22, 2019). "Michigan State basketball Cassius Winston: Only consensus preseason AP All-American". Detroit Free Press. Retrieved November 2, 2019.
^"Michigan State's Cassius Winston out with bone bruise in knee". ESPN. Associated Press. December 29, 2019. Retrieved December 30, 2019.
^Solari, Chris (January 5, 2020). "Michigan State basketball witnessed quintessential Cassius Winston; so did Michigan". Detroit Free Press. Retrieved January 5, 2020.
^"Cassius Winston's 817th career assist breaks former fellow Spartan Mateen Cleaves' record". ESPN. January 17, 2020. Retrieved January 18, 2020.
^"Big Ten Unveils Men's Basketball Postseason Honors on BTN" (Press release). Big Ten Conference. March 9, 2020. Archived from the original on March 9, 2020. Retrieved March 9, 2020.
^Dauster, Rob (March 10, 2020). "NBC Sports College Basketball All-American Teams". NBC Sports. Retrieved March 16, 2020.
^Gehring, Chris (November 28, 2020). "Wizards sign Winston to two-way contract". NBA.com. Retrieved March 30, 2021.
^Gauruder, Dana (August 20, 2021). "Wizards Re-Sign Cassius Winston To Two-Way Deal". HoopsRumors.com. Retrieved August 28, 2021.
^"Cassius Winston Stats". Basketball-Reference.com. Retrieved May 1, 2022.
^"Philadelphia 76ers 2022 NBA2K23 Summer League Roster". NBA.com. Retrieved July 5, 2022.
^"From the Washington Wizards to Munich". FC Bayern Munich. Retrieved January 28, 2022.
^"Cassius Winston Tofaş'ta". tofasspor.com (in Turkish). July 18, 2023. Retrieved July 19, 2023.
^"Pallacanestro Reggiana officially signs Cassius Winston". Sportando. July 19, 2024. Retrieved July 20, 2024.
^Borzello, Jeff (November 10, 2019). "Cassius Winston stars in Michigan State's win a day after death of brother". ESPN. Retrieved November 11, 2019.