Illegal logging is a threat to tropical forests in protected areas, yet the factors motivating it need to be better understood. Here, rural household participation in timber felling in the Barisan I Nature Reserve (West Sumatra) was described, the household contextual factors relating to this participation analysed and the importance of these activities to the household income assessed. Nearly 19% of the sampled households cut or hauled timber in the Reserve, and the demand for cash encouraged participation. Alternative livelihoods such as livestock raising and agroforestry intensification outside the Reserve could reduce the need for timber felling. Knowledge about legal status of the Reserve did not affect the odds of a household engaging in timber harvesting, but greater awareness of the Reserve resulted in lower levels of income from timber. Development policy that seeks to provide livelihood alternatives to timber felling households could reduce dependence on timber and contribute to forest conservation in the Reserve. Moreover, conservation outcomes should improve if control over the protection and enforcement of the Reserve is co-managed between the government and the local communities.