Porter was formerly managing partner for Asia, Africa, Middle East & Turkey for Mindshare and had led the WPP firm's Unilever team prior to that.
He relocated to Dubai last month after he was named media director for Unilever's North Africa and Middle East operations.
Gilmore, who has spent the last three years working on Mindshare's Unilever Asia AMET team, will now lead the agency's Unilever relationship in Southeast Asia and Japan, from the agency's regional office in Singapore.
He has spent the past two years working on Mindshare's regional Unilever team in Singapore and before that in Bangkok.
Rao, who re-located from Dubai to Mumbai in 2008, will continue to independently lead Mindshare's Unilever relationship for South Asia, covering India, Pakistan, Sri Lanka and Bangladesh.
On their appointments, Ashutosh Srivastava, CEO of Mindshare Asia-Pacific, said: "Unilever is widely recognized as an industry leader in terms of innovation and best practice in media in this region."
He added: "Both Ravi and Marc have a strong track record working on Unilever and we look forward to more breakthrough work and market firsts under the new leadership team."
In February, Unilever retained Mindshare to handle its media business in South Asia, including India, and Thailand, as well as the US, Canada, Western Europe and South and Central Europe following a six-month review process.