This species is carnivorous. It mainly eats insects such as beetles, grasshoppers, katydids, cockroaches, butterflies, moths, praying mantis, ants, phasmids, and cicadas, but also will eat small vertebrates such as bats (Chiroptera) including members of the genus "Taphozous", the lesser short-nosed fruit bat ("Cynopterus brachyotis"), and the spotted-winged fruit bat ("Balionycteris maculata"), and snakes, of which poisonous snakes have been found to be consumed. For example, the poisonous snake "Maticora intestinalis" was found to be hunted for by this species. This species was also found to consume birds, including: spiderhunters, warblers, kingfishers, and pittas. It locates prey primarily by sound and catches the prey with its hands when foraging. The prey items get killed by bites to the back of the neck and the eyes are shut when attacking. It will consume the prey starting with the head and working its way down the body. This species gets water both by drinking from a pool or stream, and by licking drops from bamboo leaves or from trunks of trees when water is running down the bark. Horsfield's tarsier is a host of the acanthocephalan intestinal parasite "Moniliformis tarsii".