Pig-tailed macaques can be found in lowland primary and secondary forests, as well as coastal, swamp, dry land, and montane forests from Burma to the Malay Peninsula and Sumatra. Some of these monkeys have been trained to harvest coconuts on plantations in these regions.

Their body hair is olive brown with white under parts. The top of their heads are dark brown, and their tails are short and slender, sometimes thinly furred and sometimes hairless. The average height for females is 18.4 to 22.2 inches; for males, it is 19.5 to 22.2 inches. Adult females average 10.4 to 24 pounds, while males weigh between 13.7 and 32 pounds.

Pig-tailed macaques live in troops of 15 to 40 individuals. The ratio is about five to eight females for each male. Males either leave the group or dwell on its periphery, while females stay in the group, living in a matrilineal hierarchy.

Sexual maturity is reached at about three years. The birth interval is between 12 and 24 months, and the gestation period is 5–6 months. The pig-tailed macaque's life span averages at 26.3 years.

 Fruit and seeds comprise 73.8% of the pig-tailed macaque's diet. Animals such as insects, nestling birds, termite eggs and larvae, and river crabs make up another 12.2%; leaves make up 5.4%, buds 3%, and flowers 1.1%. The pig-tailed macaque eats more than 160 kinds of plants.