<p>Proper solid waste management is a sustainability challenge globally, epitomised by illegal solid waste dumping particularly in developing countries. In South Africa, illegal solid waste dumping (ISWD) is a growing challenge against a backdrop of the highest inequality in the world and increasingly dysfunctional municipalities. However, there is limited research looking at the perceptions and practices regarding ISWD across a social and municipal gradient, making it difficult to inform equitable interventions. Using household interviews, this study examined practices and perceptions of ISWD across social and municipal differences in two medium-sized towns of Makhanda and Knysna in South Africa. The findings show unsustainable solid waste disposal practices including ISWD were higher in Makhanda than Knysna, and widespread among low-income households only. Recycling and composting were practiced by high-income households only. There were marked differences in perceptions of causes and impacts of ISWD between social groups. Poor municipal services and social norms were cited as the key causes of ISWD across social groups, but high-income groups also attributed ISWD to informal waste pickers. Visual pollution was perceived across social groups as the key environmental impact of ISWD, but health impacts were mentioned by low-income groups only suggesting that heterogeneity matters in addressing ISWD challenges.</p>