Cousins has also previously played for the Florida Panthers, Arizona Coyotes, Montreal Canadiens, Vegas Golden Knights, and Nashville Predators.

[6] After the Greyhounds suffered an early playoff exit in 2013, Cousins joined the Flyers' American Hockey League (AHL) affiliate, the Adirondack Phantoms, for seven games, registering just one assist on an amateur tryout contract.

[3][6] Cousins was assigned to Adirondack in September 2013 and spent the entire 2013–14 season with the Phantoms, scoring 11 goals and 29 points in 74 games.

In January 2016 Cousins and goaltender Anthony Stolarz were named to the 2016 AHL All-Star Classic as Lehigh Valley's representatives.

[11] He was recalled by Philadelphia in February to replace an injured Sean Couturier, slotting in his spot between Brayden Schenn and Sam Gagner.

He registered his first NHL point assisting on Michael Del Zotto's first period goal in a 3–2 loss to the Washington Capitals on February 7.

[16] On June 16, 2017, Cousins' five-year tenure with the Flyers organization ended as he was traded alongside goaltender Merrick Madsen to the Arizona Coyotes in exchange for forward Brendan Warren and a fifth-round choice in the 2018 NHL entry draft.

[19] He registered his first point with the Coyotes on October 21, assisting on Christian Fischer's first period goal in a 4–2 loss to the Chicago Blackhawks.

[8] In establishing a bottom-six role, providing an agitating two-way presence within the Coyotes organization, Cousins recorded a career-high 27 points (7 goals, 20 assists), in 81 games in the 2018–19 season.

[24] He made his Canadiens debut on October 17 and earned his first point with the team in the game, assisting on Victor Mete's first period goal in a 4–0 shutout win over the Minnesota Wild.

[8] On February 24, 2020, Montreal traded Cousins to the Vegas Golden Knights in exchange for a fourth-round selection in the 2021 NHL entry draft.

During the pause, Cousins returned to Canada and bonded with his teammates through daily FaceTime calls and other forms of long-distance communication.

[8][31] Leaving the Golden Knights as a free agent, on October 9, 2020, Cousins was signed to a two-year, $3 million contract with the Nashville Predators.

[33] He registered his first point with the Predators in the next game on January 16, assisting on Luke Kunin's third period goal in a 5–2 victory over the Blue Jackets.

[45] He registered his first point with the Panthers on November 6, assisting on Eetu Luostarinen's third period goal in a 5–4 loss to the Los Angeles Kings.

[8] On May 12 he scored the series-winning goal in overtime of game five against the Toronto Maple Leafs, sending the Panthers to their first Conference Final since 1996.

[50] In his second season with the Panthers in 2023–24, Cousins was involved in a series of questionable hits that led to retaliation by players on the opposing teams.

[1][2] However, the charges were withdrawn in April 2013 by the Crown Attorney's Office, which, after reviewing the evidence provided, found "no reasonable prospect of conviction.