The capital side have spent heavily this summer, bringing in the likes of Kevin Gameiro, Milan Bisevac, Blaise Matuidi and Jeremy Menez, courtesy of the financial backing of their new Qatari investors.
“For me, it's a huge pleasure to play at PSG,” said Sissoko, who has penned three-year deal with the club.
“I chose this club because it's a club with a very ambitious project and the people here have told me some very important things.”
Italian international Sirigu, who signed a four-year contract, added: “I'm very happy to be here and to be a part of such a team. I'm honoured by the interest shown in me.
“The team is going in a direction that suits me.”
Reports in both Italy and France also claim that PSG are set to beat English counterparts Chelsea to the signing of Javier Pastore.
The Argentine was in fine form for Palermo last season, which saw his stock rise considerably over the campaign.
However, Palermo President Maurizio Zamparini refused to reveal whether the 22-year-old is England or France-bound.
“The only thing that is certain is that he is going abroad,” Zamparini told Radio Radio.
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