Purpose The purpose of this paper is to analyse the drivers of sustainable entrepreneurial practices in SMEs operating in a developing economy. The secondary objectives are to explore the relationship between these drivers and to draw out the implications for policy and practice. Design/methodology/approach The paper is informed by the literature on sustainable entrepreneurship, and on the drivers of pro-environmental practices in SMEs. It reports on the results of an intensive multi-level empirical study, which investigates the environmental practices of SMEs in Pakistan’s leatherworking industry using a multiple case study design and grounded analysis, which draws on relevant institutional theory. Findings The study identifies that coercive, normative and mimetic isomorphic pressures simultaneously drive sustainable entrepreneurial activity in the majority of sample SMEs. These pressures are exerted by specific micro-, meso- and macro-level factors, ranging from international customers’ requirements to individual-level values of owners and managers. It also reveals the catalytic effect of the educational and awareness-raising activities of intermediary organisations, in tandem with the attraction of competitiveness gains, (international) environmental regulations, industrial dynamism and reputational factors. Practical implications The evidence suggests that, in countries where formal institutional mechanisms have less of an impact, intermediary organisations can perform a proto-institutional role that helps to overcome pre-existing barriers to environmental improvement by sparking sustainable entrepreneurial activity in SME populations. Originality/value The findings imply that the drivers of sustainable entrepreneurial activity do not operate in a “piecemeal” fashion, but that particular factors mediate the emergence and development of other sustainability drivers. This paper provides new insights into sustainable entrepreneurship and motivations for environmental practices in an under-researched developing economy context.