The butterflies of the Kameng Protected Area Complex in western Arunachal Pradesh, India, covering the protected areas of Eaglenest Wildlife Sanctuary, Pakke Tiger Reserve and Sessa Orchid Wildlife Sanctuary were surveyed over a 5-year period (2009–2014). A total of 421 butterfly species were recorded during the survey, including two species new to India ( Gonepteryx amintha thibetana and Bhutanitis ludlowi ) and several species rediscoveries and range extensions in the Eastern Himalaya, most notably Arhopala belphoebe , Sovia separata magna , Aulocera saraswati vishnu, Calinaga aborica, Callerebia annada annada, and Callerebria scanda opima . Here we provide an annotated checklist of butterflies of the Kameng Protected Area Complex, including historical records, distributions, abundance, habitats and other notes on these 421 species. An additional 42 species recorded in older literature or by other authors in recent times are also listed, taking the total number of species recorded in the landscape to 463.