Unsustainable palm oil production is having a devastating impact on biodiversity in producing countries in Southeast Asia. Certification schemes for sustainable palm oil have the potential to reduce these impacts. The ubiquity of palm oil in processed foods found in supermarkets is a challenge that requires intervention at the policy level and with consumers through increasing public knowledge of the problem and awareness of sustainable alternatives. Zoos are increasingly demonstrating their role in increasing awareness of multifaceted conservation issues across a range of audiences. This paper describes the evaluation of a repeat-engagement outreach programme on palm oil delivered to 7-11 year old children in UK schools by zoo educators. We conducted a mixed-method study using before-after control-treatment surveys to examine the relationship between programme participation and participants' knowledge of palm oil, sustainability, and awareness of sustainable alternatives. The analysis indicated improvements in participants' understanding of palm oil as a conservation issue, and knowledge of how and where to identify sustainable palm oil in consumer products. The analysis also indicated a smaller improvement in participants' understanding of sustainability. We discuss these findings in the context of zoo-led conservation education, and its potential role in Target-16 of the post-2020 Global Biodiversity Framework.