Former Liverpool forward Cisse joins the Stadium of Light outfit on loan while Northern Ireland international Healy has left Barclays Premier League rivals Fulham for an undisclosed fee.
Cisse has joined the north-east club with a view to a permanent deal and manager Roy Keane believes his arrival is a statement of the club's intent.
Keane told the club's official website: "This signing shows our ambitions and intentions.
"We're delighted with the new faces we've brought in, we've been working hard all summer to significantly improve the squad."
Healy has joined the Black Cats on a three-year deal. He arrived at Craven Cottage from Leeds United a year ago for a fee of £1.5million, and scored four Barclays Premier League goals last season.
Keane revealed it was the striker's international goalscoring record that impressed him. He said: "David will be a good signing for us.
"He has lots of experience at the top level and his international record is phenomenal."
Wah... Keane is a big spender... I think he has spent more money than ah ben liao and definitely Wenger liao these last 2 yrs...