Attracted by the significant additional responsibilities on offer at Loftus Road, Rigg will return to working with Mark Hughes, the former City manager and current QPR coach, a relationship that stretches back to the latter's period in charge of the Wales national team.
Rigg's remit will be to overhaul QPR's recruitment strategy by establishing a scouting network modelled on the 20-man operation he built for City.
As technical director he is also to be handed responsibility for negotiating salaries and rationalising a wage structure that does not include relegation clauses. Rigg will also assume control of QPR's academy, training ground and medical department.
Rigg, 43, spent four years at City. He was brought to the club by Hughes, who benefited at Blackburn Rovers from Rigg's data-orientated approach to player scouting.
The financial support provided by Sheikh Mansour bin Zayed allowed him to develop a worldwide scouting network that helped end the club's post-takeover dependency on agent-led recruitment.
Though the amicable nature of the departure is reflected by the fact Rigg will continue to work on City's summer transfer market strategy until the end of this month, his departure, to a club who could slip out of the Premier League, creates another senior vacancy at the Etihad Stadium.
City have been looking for a chief executive since Garry Cook was forced to resign in September. The former Barcelona technical director Txiki Bergiristain has told friends that he has been considered for a move to the club if Ferran Soriano took the post. City have said they are only looking to make one executive appointment.