Indonesia is the world’s largest producer of palm oil, and its smallholder oil palm plantations involve more than 2.3 million farmers. The rapid expansion of the oil palm area, and resulting negative environmental and social impacts, has increased the demand for sustainability certification for palm oil products. This study investigates whether different types of smallholders face different barriers in complying with certification standards. The study uses survey data from 829 smallholders in Riau, Sumatra. First, an assessment is made of the gap between current management practices and practices required by Roundtable on Sustainable Palm Oil standards for different types of smallholders. Second, the article explores explanations for the gap between current and required practices. Finally, an investigation is made of the different starting points of different types of smallholders. Results indicate that the diversity between smallholders affects their prospects for certification. To date, this diversity in smallholders has not been taken into account in the application of Roundtable on Sustainable Palm Oil standards. This can help to explain the limited success of smallholder certifications in Indonesia.