The breeding biology of Irish Dippers was studied over 12 years. A total of 501 nests was located, mostly at artificial sites, notably bridges. Irish Dippers start breeding earlier, lay fewer eggs, fledge fewer young and have fewer second broods than most other populations. The mean clutch size was 4.16 (+/-se 0.03) and the mean brood size at fledging was 3.48 (+/-se 0.05) per successful pair. The breeding biology is compared with other populations and some differences are highlighted.