Invasive species are thought to influence native biodiversity through a wide range of direct and indirect effects. We examined the influence of an invasive plant, Lantana camara, on butterfly assemblages in a tropical forest in India. Lantana camara typically dominates the understorey in invaded areas and might therefore reduce the availability of resources and microhabitats essential for butterflies. We hypothesized that butterflies would show reduced use of lantana-dominated habitat when compared with native vegetation. We evaluated such reduced habitat use by testing for (1) reduced levels of behaviours other than feeding and (2) fewer butterfly species and individuals in lantana-dominated habitat patches. To test these expectations, three plots of 30 × 30 meters each were laid in lantana-dominated and native-vegetation patches. In total, three plots in native-vegetation and three in lantana-dominated habitat were marked. Butterfly behaviour was measured through focal-animal follows, and abundance and species numbers were investigated using point sampling inside these plots. We found that butterflies showed substantial behavioural differences between lantana-dominated and native-vegetation plots, indicating a possiblity that the invaded patches were relatively less suitable for several butterfly activities. Furthermore, fewer butterfly species and individuals were seen in lantana-dominated compared with native-vegetation habitat, indicating that lantana invasion results in reduced suitability of a habitat. Whether local behavioural effects of invasive plants, such as reduced habitat use, can lead ultimately to reduced population sizes and local extinctions will need to be examined.