He attended Warroad High School,[6] where he was a star player on the hockey team for three seasons, leading the club to two Minnesota State Class A titles in 2003 and 2005.

[7] At the completion of his senior season with the Warriors in 2004–05, he attended the University of North Dakota, where he played for the Fighting Sioux.

He earned Third Team All-WCHA and received the Fighting Sioux's Cliff "Fido" Purpur Award, given to the player who demonstrates hard work and determination while generating excitement on the ice.

[7] On May 13, 2008, Oshie opted to forgo his senior season at North Dakota and signed with the St. Louis Blues.

[10] Oshie broke his ankle in a fight with Samuel Påhlsson during a blowout loss against the Columbus Blue Jackets early in the 2010–11 season on November 10, 2010, missing three months due to the injury.

[11] On July 2, 2015, Oshie was traded by the Blues to the Washington Capitals in exchange for Troy Brouwer, Pheonix Copley and a third-round draft pick in 2016.

Oshie finished the 2015–16 season with a career high 26 goals along with 25 assists for 51 points in 80 games, helping the team win their second Presidents' Trophy.

In 2016–17, Oshie would further extend his career-high in goals to 33 along with 23 assists for 56 points in 68 games en route to a second consecutive President's Trophy and third altogether for the Capitals but also another second-round playoff loss to the Penguins.

[14] Oshie saw his production drop to 18 goals, 29 assists and 47 points in 72 games in 2017–18 season but the Capitals as a team remained dominant as they would finish the season as the second seed in the Eastern Conference and once the 2018 playoffs began, Oshie would play a crucial role in the Capitals Stanley Cup victory, scoring 8 goals (including 6 on the powerplay) and 21 points in all 24 playoff games.

Oshie was sent to the training room twice, the first time requiring two stitches to a cut near his left eye created by an opponent's stick.

On January 11, 2020, Oshie was voted into the 2020 National Hockey League All-Star Game - hosted in St. Louis, home of his former team - along with Mitch Marner, Quinn Hughes, and David Perron.

On January 1, 2014, Oshie was named to the American roster for the 2014 Winter Olympics, along with Blues teammates David Backes and Kevin Shattenkirk.

[28] On February 15, in a preliminary-round game against Russia, Oshie was repeatedly selected by Team USA Head Coach Dan Bylsma to participate in a shootout that ultimately resulted in a 3–2 American victory.

[29] Oshie was the first of three shooters to face goaltender Sergei Bobrovsky in the shootout, followed by teammates James van Riemsdyk and Joe Pavelski.

After the score remained tied after the first three rounds, international rules stipulated that coaches could re-use players as often as desired.

Oshie was subsequently tabbed by Bylsma five consecutive times, ultimately converting four of six shot attempts, including the shootout-winner in the eighth round.

"[33] Oshie himself hopes his approach to ice hockey inspires others: "I think you’ve just got to enjoy the competition in playoffs.

[2] He attended the University of North Dakota in Grand Forks for three years, majoring in general studies.

After Oshie's 2018 Stanley Cup win, he remarked "My dad, he doesn't remember a lot of stuff these days.