The marine algal flora of eastern Sorsogon has been intensively collected and is generally considered as the richest in the Philippines. A trend of species records in the area has been dominated by rhodophytes (red algae) with significantly fewer similar studies for other algal groups (green and brown algae). In this study we present an updated catalogue of the green seaweeds (Ulvophyceae) of eastern Sorsogon. A checklist, including notes on taxonomy, is given of the 103 species. Twenty-six species are newly recorded locally of which five represent new records for the Philippines: Avrainvillea amadelpha, Caulerpa buginensis, an unidentified Caulerpa species, Codium cf. latum, and one taxon new to science. The new species is described as Halimeda magnicuneata Verbruggen et Dumilag based on morpho-anatomy and DNA sequence data. The number of ulvophycean species recorded in eastern Sorsogon is found to be the highest in the Philippines. This may be a result of the high collection effort in the region, as well as eastern Sorsogon’s diverse habitats providing favourable conditions for a wide range of seaweed species.