As an adolescent, he left Christian Brothers Academy in New Jersey to move to Ann Arbor, Michigan and play with the USA Hockey National Team Development Program.

Van Riemsdyk made his NHL debut in 2009, and turned a pair of strong playoff performances for the Flyers before a series of injuries kept him sidelined for most of the 2011–12 season.

He was called up to the top line that fall to replace an injured Joffrey Lupul, but remained there alongside Tyler Bozak and Phil Kessel through the 2014–15 NHL season.

In addition to his NHL career, van Riemsdyk has represented the United States at a number of international tournaments, including the 2014 Winter Olympics.

[4] His hockey career continued at Christian Brothers Academy (CBA) in Lincroft, New Jersey, where he made the varsity team as a freshman in high school.

[5] In his two seasons with the NTDP, van Riemsdyk scored 65 goals and 124 points, tying for fifth- and seventh-highest in program history at the time, respectively.

[12] Rather than immediately enter the professional leagues, van Riemsdyk chose to honor his commitment to the University of New Hampshire, where he was roommates with Capitals draft pick Phil DeSimone.

[16] On April 1, 2009, van Riemsdyk agreed to forfeit his final two years of collegiate play in order to sign an entry-level contract with the Flyers.

[19] Van Riemsdyk continued to impress Flyers coach John Stevens during training camp, scoring four goals and an assist during a September 11 preseason game against the Washington Capitals.

He regained his momentum by late December, and by January 22, van Riemsdyk was a serious contender for the Calder Memorial Trophy, awarded to the top rookie in the NHL.

[25][26] In his first playoff appearance, van Riemsdyk was part of a massive comeback effort as the Flyers, down 3–0 at the start of the 2010 Eastern Conference semifinals, battled to Game 7.

Van Riemsdyk scored his first career playoff goal in the first period of Game 7, shifting the momentum to the Flyers and helping them advance to the Eastern Conference finals.

[30] On February 15, 2011, van Riemsdyk landed his first Gordie Howe hat trick, registering a goal, an assist, and a fight in a 4–3 shootout win against the Tampa Bay Lightning.

[32] At the 2021 Eastern Conference quarterfinals, van Riemsdyk once again provided a critical Game 7 playoff performance for the Flyers, playing a role in three goals of the series-winning 5–2 win over the Buffalo Sabres.

This also interrupted the rhythm the Flyers had established with their "kid line", consisting of young forwards van Riemsdyk, Brayden Schenn, and Jakub Voráček.

[39] Following his injury-riddled season, van Riemsdyk spent the 2012 offseason as the subject of a number of trade rumors, with some sports journalists speculating that he would be sent to the Columbus Blue Jackets in exchange for Rick Nash.

[46] Van Riemsdyk began the 2013–14 season on a line with Bozak and Kessel, a trio that provided an early offensive boost to the Maple Leafs.

He moved van Riemsdyk onto a line with two-way forwards Kadri and Komarov, which strengthened all three players as they balanced offensive and defensive roles.

[57] As his recovery process dragged on, however, with van Riemsdyk still requiring crutches and a walking boot over a month later, the Leafs shut him down for the season on February 25.

[58] Van Riemsdyk entered the 2016–17 season fully healed from his foot fracture, and eager to begin playing alongside rising stars like Auston Matthews and Mitch Marner.

[71] On July 1, 2018, van Riemsdyk, who had become an unrestricted free agent at the conclusion of the 2017–18 season, signed a $35 million, five-year contract with the Philadelphia Flyers.

[74] On February 8, 2019, the NHL Department of Player Safety fined van Riemsdyk $5,000, the maximum amount allowable under the collective bargaining agreement, for a high-sticking penalty against Alec Martinez of the Los Angeles Kings.

[81] On March 4, 2020, while blocking a shot from Capitals defenseman Jonas Siegenthaler, van Riemsdyk fractured the index finger on his right hand, and he was expected to be out for the remainder of the regular season.

[89] Being placed on a line with Joel Farabee and Scott Laughton improved van Riemsdyk's scoring and playmaking abilities, as he led all NHL forwards with 4.02 assists per 60 minutes through the first 11 games of the season.

[94] As a free agent, van Riemsdyk left the Flyers for the second time in his career by signing to a one-year, $1 million contract with the Boston Bruins on July 1, 2023.

[102] In 2007, van Riemsdyk returned to the World U18 Championships, tying for the tournament lead with 12 points and helping take Team USA to a silver medal.

[119] In 2020, van Riemsdyk contributed to the PHL COVID-19 fund, aimed at providing grants to organizations serving high-risk populations in the greater Philadelphia area.

[120] In 2017, van Riemsdyk was appointed as the Maple Leafs' ambassador for the You Can Play program, an organization made to support LGBTQ individuals and reduce homophobia in sports.

[121] He told reporters that his goal as a You Can Play ambassador was to enforce respect in the greater hockey culture, and to make others "feel like idiots for thinking in a way that's archaic".

[122] Van Riemsdyk, along with fellow Flyers Scott Hartnell, Ian Laperrière, and Matt Carle, made a cameo appearance in the 2012 Judd Apatow comedy film This Is 40.