The 33-year-old ex-Glasgow and Wasps winger retired last season after more than 15 years in the game.
However, distillers Whyte & Mackay have announced a three-year deal to become official club sponsor of London Scottish and, as a brand ambassador, Logan will return to action as part of the agreement.
The club is desperate to return to the National League Division Two and Logan believes he can help their promotion bid.
He said: "I was asked if I would be keen to play again as part of the sponsorship agreement and I said I would because I would love to help them win promotion, as they are such a big club.
"But first of all I need to play and then I need to play well."
Logan will take part in Saturday's game against Old Albanians and joins an elite list of Scots - including Gavin Hastings, Damian Cronin and Iain Robertson - who have played for the club.
He added: "I was speaking with Gavin over the weekend and he was over the moon that I will be playing for London Scottish and he said they need people like myself."
Head coach Rowly Williams agreed, saying: "Getting somebody of Kenny's quality at this stage is a huge boost to our goal of reaching higher National League status."