Many tropical regions are experiencing a rapid growth of oil palm cultivation. In Indonesia, the world's leading palm oil producer, in addition to large companies, smallholder farmers are increasingly engaged in the oil palm sector. Smallholder oil palm cultivation may contribute to income gains and socio‐economic development. However, land‐use decisions by smallholders are not well understood. Without appropriate policies, negative social and environmental consequences can also occur. To improve the knowledge base, we use data about present and past land‐use decisions from a survey of farm households in Sumatra. Employing duration models, we analyse the determinants and dynamics of oil palm adoption among smallholders. We find that independently operating farmers are currently driving growth rates in the oil palm sector. Smallholder adoption decisions are mainly attributable to regional and village level factors. While the current adoption primarily occurs outside of contracts, previous contractual ties between companies and other farmers in the same village play an important role for individual decisions. Beyond initial adoption, we also analyse later expansion decisions. While expanding the oil palm area subsequent to initial adoption is common among all types of adopters, those without previous contracts are found to expand significantly faster. We conclude that the concessions the government has allocated to palm oil companies in the past have initiated oil palm adoption in the small farm sector, but that the ensuing land‐use dynamics are mostly beyond government control. Some wider implications are discussed.