Reporting directly to Malcolm Poynton, the executive creative director of O&M, Graham joins O&M's other creative partners - Dennis Lewis, Neil Dawson, Greg Burke and Richard Russell - in running the department.
Poynton said: "Since starting in this role, I have wanted to appoint five creative partners. It has taken me two years to do this because I didn't want to employ just anybody. The people have to be the right fit. Alasdair is a great communicator who is not looking for fame - he lets his work do the talking, which is what our clients want."
In the past seven years at TBWA, Graham has worked on accounts including the One Account, Whiskas and PlayStation, for which he created the "fun, anyone?" campaign.
Before TBWA, he spent nine years at BMP DDB Needham, where he worked on Volkswagen and Nicorette.
Poynton added: "Alasdair has created some wonderful work for major clients during his career. This is why he will be a great fit for the agency. We have proven we can produce great work on a handful of big clients, such as Dove and Castrol, but we have a lot more major clients we need to offer this level of service to."
Graham's hiring follows the appointment earlier in March of Russell Jarman Price and Alex Gulland. The pair will head a non-traditional creative solutions arm focusing on broadcast content, media promotions and experiential marketing.