In 2015 the Pacific Ocean experienced a strong El Niño Southern Oscillation (ENSO). With this change in water temperature, marine species were able to expand outside their previous ranges and settle in new habitats. The first sighting of the species Labrisomus xanti, or largemouth blenny, on Santa Catalina Island was October 2015 and since then the species has been seen regularly around the island. In October and November of 2018, we surveyed three sites along the leeward side of Catalina Island. Largemouth blennies were counted, measured, and sex determined along diver transects at multiple depth strata. Substrate type was also recorded. We observed multiple sizes of largemouth blennies among sites, depths and between sexes. Among the three sampled locations, Empire Landing had significantly more individuals than Big Fisherman Cove and Yellowtail Point. These differences were likely due to the greater abundance of small and medium-sized boulders and lack of sand patches within the rocky reef at Empire Landing. Male largemouth blennies were significantly larger than females. The largest largemouth blennies were found at a depth of 4.5 m with the smallest individuals found in the shallow (1.5 m) depths. Individuals were significantly larger at Empire Landing and Yellowtail Point than at Big Fisherman Cove. Finally, length frequency analysis identified at least four putative age classes corresponding to the years 2014–2017 supporting a well-established population. However, further study is necessary before we can determine whether the population at Catalina Island is a self-sustaining population.