Species diversity of chrysomelid beetles (Coleoptera) was studied in forest ecosystems of Guilan province, northern Iran. Sampling was conducted by sweep net, aspirator and Malaise trap during 2009-2012. A total of 15 species in five subfamilies- Bruchinae (2 species), Cassidinae (3), Criocerinae (2), Donacinae (3) and Galerucinae (5) were identified. Among the collected species 12 are new records for the Chrysomelidae fauna of Iran: Bruchidius canescens (Motschulsky, 1874), B. fulvescens (Baudi di Selve, 1886), Cassida flaveola Thunberg, 1794, C. inquinata Brulle, 1832, C. stigmatica Suffrian, 1844, Crioceris quatuordecimpunctata (Scopoli, 1763), Oulema tristis (Herbst, 1786), Donacia clavipes clavipes Fabricius, 1792, D. simplex Fabricius, 1775, D. tomentosa Ahrens, 1810, Galerucella calmariensis (Linnaeus, 1767) and Exosoma flavipes (Heyden, 1878). All the species are presented with data on their general distribution and the material examined.