Continuity mistake: Just before Declan and Anna are going to sleep in the B&B, when she agrees he can sleep in the same bed he is holding a pillow. He then puts the pillow on the bed and the pattern on his and hers pillows are on the left side, however the next scene shows that his pillow pattern is on the right. (00:56:55)
Continuity mistake: When Anna is left on the beach by the fishing boat, you can see the boat is directly in line with her as it leaves. In the next shot however, the fishing boat is now significantly to the left of her, having not had the time to achieve it.
Continuity mistake: When Declan is having his whiskey poured at the table with the Italian couple, his arms are crossed in front of him, but when the camera cuts to a wider shot, his right arm is now by his side. Camera cuts back to closeup and his arms are folded again.
Factual error: Towards the end of the movie where they finally can get on the bus the bus scene has two mistakes. One is that it travels ilegally on the right hand side of the road at speed over some chevrons but more importantly as they are supposed to be in Tipperary, there is a bus stop sign which says "Dublin City Bus" which is a completely different bus service to the "Bus Eireann" service they get on.
Factual error: It's meant to be set at the end of February but it seems to be spring/summer throughout (the best bit being the picking of carrots while staying in the guest house - definitely not an early cropper in the UK, and I'm sure not different in Ireland).
Factual error: When they arrive at Dingle in the boat, Dingle has a large dock for fishing boats - so it would be ludicrous to be dropped on a beach.
Revealing mistake: When Declan and Amy miss the bus to Dublin the morning after the wedding, Amy walks out of the restaurant Poppie's Country Cooking with coffee. That restaurant is actually located in Dublin. (01:00:13)