Below is an easy comparison table that will show you the major differences between old world monkeys and new world monkeys.
| New World Monkeys | Old World Monkeys | |
| Size | Small to medium sized primates | Medium to large sized primates |
| Nose | Scientific name for New World Monkeys is Platyrrhini which means “flat nosed”. Nostrils face sideways | Scientific name for Old World monkeys is Catarrhines which means “narrow nosed”. Nostrils face downwards. |
| Tail | Phrehensile tail (used like a 5th leg) | Non-grasping tails |
| Vision | Lack trichromatic vision (mono vision) – exception: Howler Monkey | trichromatic vision (color vision) |
| Dental | 12 premolars | 8 premolars |
| Butt | No Pads | Have a pad for sitting |
| Trees | Primary tree dwellers | More varied habitat from rainforest to desert |
| Thumbs | Thumb sits in line with other fingers | Opposable thumbs |
| Pairing | Form more monogamous pair bonds / both show substantial paternal care of young | Less monogamous |
| Species | Marmosets Taramins Howler Monkeys Spider Monkeys Woollys Titi Monkey Capuchins Squirrel Monkeys Owl Monkeys Sakis Uakaris |
Baboons Guenons Macaques Mangabeys Patas Colobus Langurs Leaf-monkeys Proboscids |