— Sens Communications (@Media_Sens) September 19, 2021
The tryout will begin when Ottawa's training camp gets underway Wednesday.
Ennis, 31, played 61 games with the Senators in 2019-20 and recorded 14 goals and 19 assists. He was then traded at the deadline in exchange for a fifth-round pick to his hometown of Edmonton to play with the Oilers, where he's played since.
Last season, Ennis scored three goals and added six assists in 30 games with the Oilers.
A 26th overall pick by the Buffalo Sabres in 2008, Ennis has also played for the Sabres, Minnesota Wild and Toronto Maple Leafs.