Anaikatty Hills of the Western Ghats in Tamil Nadu witness the annual spectacle of mass movement of lakhs of butterflies. The present paper examines the impact of vehicular traffic on this ‘butterfly migration’ through a survey of butterfly mortality along a road stretch in Anaikatty Hills. A high rate of mortality due to road traffic was observed during the mass movement of butterflies. One-hundred-and-thirty-five butterfly road kills belonging to three families, nine genera and 12 species were recorded during the study. The proportion of nymphalid butterflies among the road kills (70%) was very high compared to their respective share in the background population (39%), indicating a higher road mortality risk for nymphalids. The conservation significance of the road traffic impact on butterfly assemblage and management options are discussed.