Farrell already has a role with the Thames Gateway, and one in Edinburgh. He will now work with recently announced Outer London Commissioner William McKee.
Johnson said: "For too many years the focus of the previous mayoralty was channelled towards inner London. The vital role played by our town centres and communities in the suburbs has been overlooked, if not ignored, to the detriment of all Londoners."
The new Commission, which will have up to 12 members, will advise the Mayor on the London Plan and identify up to five areas to become outer 'London growth hubs'.
Terry Farrell said: "London's outer boroughs cannot afford to be overlooked as they contain some of the most important drivers of London's future success. In looking at outer London it is important, of course, to look at London as a whole, and that is how I intend to help the Mayor and the commission as it develops real projects for the benefit of the capital."