Severe losses in biodiversity hotspots reduce global insect diversity. Renosterveld is a critically endangered and biologically diverse ecosystem occurring only in the fynbos biome of the Cape Floristic Region (CFR), a recognized global biodiversity hotspot. Following agricultural intensification, less than 5% natural renosterveld vegetation remains in the Swartland of South Africa’s Western Cape. Remaining renosterveld is highly fragmented and confined to land less suited to agriculture, including steep slopes and rocky outcrops. These fragments vary in their environmental conditions at the local (e.g. microhabitat, floral diversity and density) and the landscape (e.g. patch size, habitat connectivity and surrounding crop cover) level. The influence of these environmental variables on butterfly diversity at a landscape scale in the CFR is not fully understood. We selected 32 sites across the Swartland and surveyed for butterflies to determine the effect of environmental variables on butterfly diversity, specifically butterfly species richness, abundance and composition. Overall, we found 2861 individuals of 27 species. Our findings suggest that crop cover in the surrounding landscape affects butterfly diversity at a small landscape scale (< 500 m radius) in the CFR. Flower species richness and microhabitat type impact species richness and abundance. Patch size is a key predictor of species diversity particularly for endemics and site quality may influence species composition. All renosterveld patches regardless of size and site quality can be considered valuable for butterflies in this highly fragmented landscape.