The TV ads, created by DDB London, feature Paddington replacing his trademark marmalade sandwich with one containing Marmite and cheese.
The multimillion-pound campaign will run across TV and radio throughout October as part of Marmite's long-running 'Love it or hate it' marketing strategy.
Last summer, Marmite launched an upside-down squeezy variant which it backed through a £3m advertising campaign by DDB. The introduction of the bottle was the biggest change to the brand in its 104-year history.