The Blackhawks sent Dylan Sikura to Vegas for the 29-year-old Pirri, who split last season between the Golden Knights and Chicago of the American Hockey League. The forward had two assists in 16 games with Vegas, and 15 goals and 20 assists in 38 games with Chicago.
Pirri was selected by the Blackhawks in the second round of the 2009 draft and made his NHL debut with the club in 2010. He had a career-high 22 goals for Florida during the 2014-15 season.
Pirri is signed through the 2020-21 season with a salary-cap hit of $775,000.
The 25-year-old Sikura had one goal and 13 assists in 47 games with Chicago over the past three seasons. He was a sixth-round pick by the Blackhawks in 2014.