The 24-year-old forward had three points (one goal, two assists) in 15 games for the Florida Panthers this season and missed 28 games with an upper-body injury.
Hawryluk is expected to join the Senators (20-28-11) when they host the Buffalo Sabres at Canadian Tire Centre on Tuesday (TSN5, RDS2, MSG-B, NHL.TV).
"Jayce Hawryluk is a highly competitive two-way forward," Senators general manager Pierre Dorion said. "He's an energetic, puck pursuit-type player who should mesh well under [coach] D.J. Smith and our current roster."
Hawryluk has 15 points (eight goals, seven assists) in 67 games during two NHL seasons with the Panthers, who selected him in the second round (No. 32) of the 2014 NHL Draft.
