Originally selected by the Montreal Canadiens in 2010 (117th overall),[6] Ellis was signed to a three-year, entry-level contract by the Canadiens on March 1, 2012.[7] In 2012–13, his first professional season, he was assigned to play in the American Hockey League (AHL) with the Hamilton Bulldogs, skating in 71 games and registering four goals and four assists for eight points, along with 57 penalty minutes.[8]
On June 1, 2015, Ellis was signed to a one-year, two-way contract extension by the Canadiens.[9] On January 27, 2016, he was named to represent the North Division roster for the AHL All-Star Game while member of the Canadiens newfound AHL affiliate, the St. John's IceCaps.[10]
On February 26, 2016, Ellis was recalled by the Canadiens and played in his first National Hockey League (NHL) game on March 2, 2016,[11] in a 3–2 shootout loss to the Anaheim Ducks at the Honda Center.[12] He would play two additional NHL games before being reassigned to the IceCaps on March 6, 2016.[13]
On July 2, 2016, having left the Canadiens organization as a free agent, Ellis agreed to a one-year, two-way deal with the St. Louis Blues.[14] After competing in the Blues' 2016 training camp, he was assigned to AHL affiliate, the Chicago Wolves, for the duration of the 2016–17 season.[8]
Once again a free agent at season's end, Ellis moved to the Deutsche Eishockey Liga (DEL), agreeing to a one-year contract with German outfit Kölner Haie on May 9, 2018.[17]
Ellis continued his journeyman European career in 2019–20, signing a one-year contract with Russian club HC Sochi of the Kontinental Hockey League (KHL) on May 2, 2019.[18] At the conclusion of his contract in Sochi, he remained in the KHL by securing a one-year deal with Latvian-based club Dinamo Riga on August 3, 2020.[19]
In the 2020–21 season, Ellis began the year as an alternate captain with Riga, posting a goal and three points through 17 games. However, on November 30, 2020, Ellis would leave the KHL and return to Germany, signing for the remainder of the DEL season with ERC Ingolstadt.[20]
Following three seasons with Eisbären Berlin in which he won two league championships, Ellis returned to ERC Ingolstadt in July 2024, inking a one-year contract for the 2024–25 season.[23]
^"ERC HOLT WEITEREN TOP-VERTEIDIGER" [ERC BRINGS IN ANOTHER TOP DEFENSEMAN]. ERC Ingolstadt (in German). November 30, 2020. Retrieved November 30, 2020.
^"Morgan Ellis kommt nach Berlin" [Morgan Ellis is coming to Berlin]. Eisbären Berlin (in German). May 26, 2021. Retrieved July 26, 2024.
^"Erste Personalentscheidungen" [First personnel decisions]. Eisbären Berlin (in German). March 16, 2023. Retrieved July 26, 2024.
^"ELLIS WIEDER EIN PANTHER" [ELLIS AGAIN A PANTHER]. ERC Ingolstadt (in German). July 10, 2024. Retrieved July 26, 2024.