The brewer will be sending out RFIs so that it can shortlist agencies for the RFP stage and is expected to make a decision before March next year.
MillerCoors, a joint venture between Molson Coors and SAB Miller, is soon to be rolled into Molson Coors.
The company has worked with Zenith in the UK since 2009. Initiative is its media agency in the US, and MEC in Canada.
Molson Coors’ portfolio of brands includes Carling, Doom Bar, Coors and Cobra.
A spokesman for Molson Coors said: "Molson Coors continually reviews its agency partners to ensure it has the best operators to build its portfolio across the globe.
"We can confirm that we are undertaking a review for our media agency partner across the US, Canada & UK but will not comment further while the process is on-going."