Wijnaldum was brought in by the Magpies during the summer transfer window, and he has made a positive impression at St. James' Park.
The attacking midfielder's power and skill has seen him go straight into Newcastle's starting line-up, and he rewarded Steve McClaren's faith by scoring four goals in his side's 6-2 win over Norwich City at the weekend.
And Sissoko said: "I'm happy for Gini. He works so hard in training and is a fantastic player for us.
"I hope he can continue in this and keep scoring goals for us because he is a big player."
Sissoko assisted Wijnaldum for two of his goals in the 6-2 triumph, and Newcastle will hope that their partnership can continue to cause problems.
McClaren's side have been out of sorts throughout the campaign so far, but they showed their quality on Sunday and finally have some momentum building behind them.
Newcastle are now just two points adrift of safety, and they have moved into 18th place as a result of their crushing victory over the Canaries.
They now have a huge derby match against Sunderland to focus on, and know that if they are able to pick up three points against their struggling rivals, then they could be out of the relegation zone by the end of next weekend.