Irish waters represent one of the most important marine habitats for seabirds in Europe and are utilized by a wide range of seabird species. However, the at-sea abundance and distribution of many of the seabird species occurring in Irish waters remains poorly understood. Under the EU Birds Directive, there is a requirement on member states to conduct surveillance of seabirds occurring within their waters. The Department of Arts, Heritage and the Gaeltacht (DAHG), through the Marine Institute, commissioned a seabird survey from the MRV Celtic Explorer during the annual Celtic Sea Herring Acoustic Survey (CSHAS), running from the 4th to the 24th of October 2020. A standard line transect survey methodology was employed by the seabird observer with additional visual point sampling at fishing locations and oceanographic sampling stations. Survey transects were undertaken at speeds of 5-10 knots, with fishing activity being conducted at speeds of 2-3 knots. The seabird observer’s survey effort was maximized and optimized during periods of sea state less than or equal to sea state 6 and with visibility of greater than 300m. A total of 117 hours and 34 minutes of survey effort was conducted over the course of the CSHAS 2020 survey. In total, 99 hours and 50 minutes of survey effort were conducted using a line transect methodology, while 14 hours and 45 minutes of effort were conducted using the point sampling methodology. A further 2 hours and 58 minutes of effort were conducted as a casual watch. A total of 3764 seabird sightings were recorded throughout the survey, totalling 35639 individuals. In total, 11624 seabirds were recorded as “in transect”, while 24012 were recorded “off transect”. The species encountered included 27 species from 9 families. A further 74 sightings of terrestrial birds were also recorded, comprising of 287 individuals.