 On June 23, 2017, after seven seasons with the Blues, Reaves was traded to the Pittsburgh Penguins along with a second-round pick (51st overall) in the 2017 NHL Entry Draft in exchange for Oskar Sundqvist and the Penguins' first-round pick (31st overall) in the 2017 draft.In the 2017–18 season, Reaves added muscle to the Penguins lower lines, providing 4 goals and 8 points in 58 games.On February 23, 2018, Reaves was involved in a trade with the Vegas Golden Knights.