The trade was announced following Toronto’s 5-3 loss to the New York Rangers Wednesday night.
L.A. receives Toronto’s third-round pick in 2020, which was previously acquired from Ottawa on July 1, 2019, and a conditional third-round pick in 2021.
The Kings will retain 50 per cent of Clifford’s salary as part of the transaction.
Campbell, 28, has appeared in 57 career NHL games with Los Angeles and one game with Dallas. The Port Huron, Mich., native has compiled a career record of 20-25-5 with a 2.58 goals-against average and a .916 save percentage.
Campbell was originally selected by the Stars in the first round (11th overall) of the 2010 NHL draft.
Clifford, 29, has appeared in 660 career NHL games, all with Los Angeles, and recorded 129 career points (60 goals, 69 assists). The Ayr, Ont., native is a two-time Stanley Cup champion, winning with the Kings in both 2012 and 2014.
Clifford was originally drafted by Los Angeles in the second round (35th overall) in 2009.