The 24-times capped threequarter will combine playing for the English Championship club from next season while taking up a new career in the City.
Vernon, 30, was called into the Scotland squad for the 2018 Natwest Six Nations match against Italy but did not play in Rome. His last cap came in 2015.
London Scottish chairman Malcolm Offord said: “This is a significant signing for London Scottish. Richie is an international rugby player and to have him in our squad next season is a real statement of aspiration for the club.
“I have been so impressed by Richie’s drive to continue playing top level sport while preparing for life after rugby. We are looking forward to working with Richie and helping him with his transition into a career in the City.”
Vernon told the London Scottish website: “I’m really excited to join London Scottish. I enjoyed hearing the vision that the management have for the club and was immediately convinced it was the right move. This unique opportunity was too good to pass up.”
Vernon has the rare distinction of having appeared at two separate World Cups, one - in 2011 – as a forward, and the other - in 2015 - as a back.