Abstract Background Smallholding plantations represent approximately 40% of the total palm oil plantation area globally. For any certifications, standards, and other instruments to achieve more ethical and sustainable palm oil supply chains, it is essential to improve smallholder engagement in the schemes. A large body of research has built up our understanding of the challenges of engaging smallholders in sustainability initiatives in various sites and countries. A broad systematic understanding of how different types of sustainability initiatives can support or restrict smallholders from access to market and different resources and under which economic and social conditions are not yet developed. This systematic map aims to identify, map, and describe the body of evidence that exists on the positive and negative impacts of sustainability initiatives on smallholder engagement in palm oil practices in Southeast Asia. The findings are expected to inform policies and practices on smallholder engagement in sustainable palm oil supply chains and identify evidence gaps where future primary studies and evidence syntheses can contribute. Methods We will develop a guiding framework of interventions through other works on supply chain instruments. We will then construct a test library of 39 items through field expert consultations and snowballing using literature search algorithms. The search will cover four publication databases, five bibliographic databases, and 13 topical and organizational websites. We will search for existing evidence syntheses and primary research studies in Southeast Asia countries published between 2008 and 2021. This systematic map will only include English language articles due to our limited capacity. We will screen the search results at the title/abstract and the full-text levels. Numbers of included/excluded items and reasons for exclusion will be noted and visualized via a ROSES flow diagram. We will develop a data extraction form for assessing data useful for reporting current trends of smallholder engagement in sustainable palm oil initiatives. A random sample of 20% of the included articles will be assessed for validity using Joanne Briggs Institute’s critical appraisal checklist. We will then organize and summarize the data according to the defined PICO.