"I worked with Ola at PSV (Eindhoven) so I know him well," Sunderland manager Dick Advocaat told the club's website (www.safc.com).
"He is a national team player with a lot of experience, an attacking midfielder who can score goals and is good in the air -- he will bring something different to the team."
Toivonen was at Dutch champions PSV from 2009-14, winning the KNVB Cup and Dutch Super Cup with the club.
The player could make his debut this weekend when the Black Cats travel to Aston Villa in the Premier League on Saturday, Sunderland said.
(Reporting by Simon Jennings in Bengaluru; Editing by John O'Brien)
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