The cultivation of palm oil has many adverse social and environmental impacts. The high level of biodiversity that is native to areas where palm oil plantations occur is at risk. Various measures are taken, such as the Roundtable of Sustainable Palm Oil (RSPO). The RSPO certification is a sector governance measure that indicates which management and operations interventions have to be implemented to protect the public interest – countering negative social and environmental impacts. No research has been done on the impact of RSPO certification and the plantation size on biodiversity. The research question of this thesis is “do RSPO certification and plantation size influence the level of biodiversity of palm oil plantations in Indonesia and Malaysia?” Three open source online data sets from Global Forest Watch containing information on plantations were used. These spatial data sets were combined with Global Biodiversity Information Facility (GBIF) species observations data. From GBIF, four taxa were selected to be used in this study, known to be impacted by palm oil cultivation: birds, lizards, primates and small mammals. The majority of the GBIF observations that laid within the studied plantation data set, however, were bird observations (93.0%). Only 1.8% of the GBIF observations laid within the palm oil plantations. Data analysis indicated that there is no significant difference between RSPO and non-RSPO-certified plantations in terms of biodiversity. The obtained results imply that the measures that are taken by plantations to obtain the RSPO certificate do not affect the level of biodiversity and therefore certification does not protect the species living on plantations better when compared to plantations that are not RSPO-certified. Results also indicate that biodiversity is not influenced by the size of a plantation – small, medium or large. The proposed research was the first attempt in getting insight into the effectiveness of certification and small-scaled plantations – in other words plantation size – on biodiversity levels. It can be concluded that the effectiveness of the two measures has not been proven yet. Suggestions for further research are done, in which higher quality data sets and larger numbers of observations are of importance.