The 28-year-old stand-off has made 16 appearances for Wasps after recovering from a ruptured anterior cruciate ligament and won his 28th Scotland cap during this year’s RBS Six Nations.
Dai Young, director of rugby at the Ricoh Arena, told wasps.co.uk: “Ruaridh is a very talented player and we were obviously keen to keep him.
“He was certainly part of our long-term plans, but we appreciate he was keen to secure the most game-time possible and he felt this would be elsewhere given the 10s we will have here at Wasps next season. We will part on good terms and wish him the very best at Quins next season.
“Ruaridh is a great guy, who is extremely popular within the squad and is highly respected for his skill-set and his commitment to the team and to helping the squad succeed.”
Jackson, who joined Wasps from Glasgow Warriors in 2014, added: “It was an extremely tough decision to leave Wasps having loved my two years here.
“It’s a club on the up, playing great rugby, but I feel this move is the best decision for my career.
“I’d like to thank Dai especially for understanding my decision and letting me go, and wish the very best to everyone associated with the club.”
Jackson was part of Scotland’s World Cup training squad last year but did not make the final 31 for the tournament. He forced his way back into the reckoning for this year’s Six Nations and featured against Wales in Cardiff, coming on as a replacement at full-back when Stuart Hogg was injured early on.