The 29-year-old was a member of the Springboks squad that won the 2007 World Cup and he also played in the 2011 and 2015 tournaments.
"We have been looking to add world-class quality throughout the squad and JP is certainly in that class," Leicester director of rugby Richard Cockerill said.
"He has played at the very highest levels of the game for a long time ...and is keen to experience club rugby in Europe."
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Leicester are one of English rugby's most successful teams and have twice been European champions. They last won the Premiership title in 2013 and lie fourth in the table mid-way through the season.
Pietersen, currently playing in Japan, has scored 22 tries in 66 internationals. He will join Leicester after the end of this year's southern hemisphere Super Rugby club competition, in which he will play for the Natal-based Sharks.
"I'm really looking forward to joining up with a quality team like Leicester Tigers and competing for silverware in the Premiership and European Cup," Pietersen said.
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