The two restaurants have been locked in a long legal battle
Supermac's is embarking on a new kind of marketing campaign.
The Irish fastfood chain is putting adverts, on the side of trucks, outside its rival McDonald's.
In a clear dig against the US firm, one advert reads: "No clowning around, just great food!".
This is accompanied with an image of McDonald's mascot, Ronald McDonald, upside down in a rubbish bin.
This was spotted outside a McDonald's in Galway:
Supermac's has also posted the advert on their Facebook page:
The two fast-food firms have been locked in a long legal battle over the right to use the 'Supermac's' name outside of Ireland.
McDonald's has objected to the use of the name, and has accused the Irish firm of trying to piggy-back on its brand.
The Irish firm's international plans were put on hold after McDonald's successfully argued that having a 'Mac' competitor would create confusion for customers across the EU and in Australia.
Supermac's has asked the EU regulator to cancel the use of the Big Mac trademark registered by McDonald's under certain classes.
The request has been formally submitted to the European Union Intellectual Property Office (EUIPO).
Managing director of Supermacs, Pat McDonagh, told Newstalk.com: "McDonald's have announced that they're moving their head office from Ireland to the UK - so I suppose really that's pretty questionable in our eyes.
"They have changed the green jersey to another jersey.
"Does that mean they're going to stop buying Irish beef? Does it mean they're moving all their logistics to the UK, etc?".
He also said they will be doing more advertising around the country, but was not in a position to give further details.