Kefu, a former Australian international centre, joins from French side Castres, England cap Varndell moves to Adams Park from perennial rivals Leicester Tigers and Ward-Smith joins from the Guinness Premiership's bottom club, Bristol.
Varndell has finished as Leicester's top tryscorer in each of the last three campaigns and currently has three international tries in four appearances for his country to his name. Ward-Smith was one of the stars of 2006 before injury cruelly denied him a first England cap and a place in his country's 2007 World Cup squad, while Kefu won six caps for the Wallabies between 2001 and 2003.
"As a club we are delighted with these three outstanding signings," said McGeechan, who led Wasps to the English title last season.
"Dan Ward-Smith is one of the strongest back row carriers in the Guinness Premiership and a very high-quality player who we are delighted to have join us. We have a great history of back row players at the Club and we know he is going to add a lot to the squad.
"Tom Varndell is a very exciting signing for us. Probably one of the most promising young wingers in the game and at just 23 we feel he will bring a lot again to the way Wasps want to play.
"Steve Kefu provides us with the experience we want to replace Riki Flutey at 12. Not a dissimilar player, his experience will be a great benefit to the squad and will be very good for our younger players.
"With both Tom and Dan recognised by the international set up over the course of their careers, it would give us great satisfaction to see them follow so many players who have joined this Club and go on to put on an England shirt. They are both great talents with great potential for both Club and country and as coaches we look forward to working with all three of these players next season."