While low serotonergic activity is often associated with psychological disorders like depression, anxiety, mood and personality disorders, variations in serotonin also contribute to normal personality differences. Here we investigate the role of blood DNA methylation levels at individual CpG sites of two key serotonergic genes (serotonin receptor gene 1A, HTR1A; serotonin transporter gene, SLC6A4) in predicting personality of captive chimpanzees. We find associations between methylation at 9/48 CpG sites with four personality dimensions: Dominance, Reactivity/Dependability, Agreeableness and Openness. Directionality of effects were CpG location-dependent and confirmed a role of serotonergic methylation in reducing anxiety (Dominance) and aggression related personality (Reactivity/Undependability) while simultaneously promoting prosocial (Agreeableness) and exploratory personality (Openness). While early-life adversity has been shown to impact serotonergic methylation patterns in other species, here, atypical early social rearing experiences only had a modest impact on CpG methylation levels in this chimpanzee sample. While the precise environmental factors impacting serotonergic methylation in chimpanzees thus remain to be identified, our study suggests a role in shaping natural variation in animal personality. The results of this study offer a basis for future hypothesis driven testing in additional populations and species to better understand the impact of ecology and evolution on complex behavioral traits.