The 27-year-old is part of the Pakistan ODI squad touring England and recently scored 152 in a ODI against Ireland, as well as 58 off 30 balls in the match with England at Trent Bridge.
He will be available for all of Leicestershire's T20 campaign.
"Sharjeel is a powerful hitter who will offer another option," chief executive Wasim Khan said.
"We have been watching him closely this summer, where he has caught the eye with his dynamic ball striking."
Pakistan one-day batsman Sharjeel Khan is joining Leicestershire to play in the T20 Blast for the 2017 season.