Three species of nematodes (Acuariidae) were recovered from a total of 108 adult and chick Olrog's Gulls, Larus atlanticus. Birds were collected from a breeding colony in the Bahía Blanca estuary of Argentina, during the breeding seasons of 2005 (n  =  66 chicks, 3 adults), 2006 (n  =  37 chicks, 1 adult), and 2007 (n  =  1 chick). Nematodes were identified as Pectinospirura argentata, Skrjabinoclava andersoni, and Sciadiocara sp., and all represent new host and locality records. Prevalence of infection among chicks during the 2005 and 2006 breeding seasons was 80.3% and 89.2%, respectively, and 67% for adults in 2005. Also, third-stage acuarid nematodes were found in possible intermediate hosts, Neohelice granulata (Crustacea: Decapoda) and Cyrtograpsus angulatus (Crustacea: Decapoda).