Understanding how vervet monkeys (Chlorocebus pygerythrus) select resources provides information for effectively managing them and the environments they live in, which may reduce conflict with humans. This study investigates resource selection on woody plant species by two vervet monkey (vervet) troops living in human-modified mixed-broadleaf savanna in South Africa. Our findings indicate that one troop's home range was more diverse in terms of woody plant species than the other. No relationship between the frequency of occurrence of resource items in the diet and the availability of those items was found for either troop, suggesting that food selection is not based on availability. However, resource items were selected in proportion to their energy content, indicating that vervets are potentially energy maximizers (species that select resource items based on energy content). This was noticeable for the vervets living in the more diverse home range. Vervets in the less diverse home range displayed less clear preference for higher energy food items. Despite this disparity between the troops, our findings suggest that both troops used whatever resource items were available to them, and that it is important to maximize the tree diversity in vervet habitats to ensure population persistence and reduce conflict with humans.