Academy graduate Griffin, who has been capped by Ireland Under-20s, underlined his potential with his man-of-the-match performance against Samoa in 2010.
Griffin's midfield partner McSharry came through the ranks at Leinster before moving to Galway in the summer - however the 21-year-old has made an immediate impression.
And Griffin is delighted to have sorted out his future at his hometown club.
"Well I'm from here so I'm delighted to be playing for Connacht and with Dave for another two years," he said.
"Hopefully that will go well, we have played together (Ireland U20s) so I'm really happy."
McSharry added: "The best way to develop for us young lads is playing games and that's what we are getting to do here, I'm delighted.
"I had no hesitation when the contract was put in front of me. I have played in a few huge games now and those games can do wonders for you. Playing in those big games is worth 10 training sessions. This is what I want to be doing, playing as much as possible."