The Senators reportedly give up a fifth-round pick in the draft this summer, and a third rounder in 2015.
Hemsky has scored 142 goals and 335 assists for 477 points in 652 career regular-season games, with 303 penalty minutes.
He scored six goals and 11 assists in 24 games when Edmonton reached the Stanley Cup final in 2006, but hasn't been back to the playoffs since.
The 30-year-old from Pardubice represented the Czech Republic at the recent Sochi Games, his second time representing his country at the Winter Olympics.
Originally selected 13th overall in the draft, Hemsky is in the final year of a deal that represents a $5 million US salary cap hit.