McDonagh also competes internationally for the United States and was a member of the men's ice hockey team at the 2014 Winter Olympics in Sochi.

[4] On June 30, 2009, McDonagh was traded (along with Chris Higgins, Pavel Valentenko and Doug Janik) to the New York Rangers in exchange for Scott Gomez, Tom Pyatt and Michael Busto.

[11][12] On March 20, McDonagh was the victim of an elbow to the head from Pittsburgh Penguins forward Matt Cooke, who was subsequently suspended for the remainder of the regular season and the first round of the 2011 Stanley Cup playoffs.

[13] On April 9, 2011, McDonagh scored the game-winning goal, the first of his career, against the New Jersey Devils, earning the Rangers the eighth and final playoff spot in the Eastern Conference.

[14] As a result of the 2012–13 NHL lockout, McDonagh signed a contract with Barys Astana of the Kontinental Hockey League (KHL).

[17] The team defeated the Philadelphia Flyers, Pittsburgh Penguins and Montreal Canadiens en route to the 2014 Stanley Cup Finals against the Los Angeles Kings, where the Rangers lost the series 4–1.

In his first season as captain, he led his team to the Presidents' Trophy and were ultimately eliminated in the Eastern Conference Finals by the Tampa Bay Lightning in seven games.

[22] McDonagh missed eight games as a result, including a February 14 rematch between the two teams, during which Rangers' rookie defenseman Dylan McIlrath fought Simmonds.

[27] On July 19, 2013, McDonagh married long-time girlfriend Kaylee Keys at Our Lady of Victory Chapel in his hometown of Saint Paul, Minnesota.

[29] After being drafted, McDonagh attended the University of Wisconsin–Madison for three seasons, playing with their ice hockey team, before foregoing his final year to turn pro with the Rangers.

In January 2021, McDonagh re-enrolled with the school, taking online classes to complete his final 18 credits and graduate with a degree in Personal Finance.