Apes, human's closest living relatives, are renowned for their intentional and highly flexible use of gestural signals In stark contrast, evidence for intentional signalling in monkeys is scant, especially when considering signals produced amongst conspecifics. We present data on the naturally occurring gestural communication amongst captive red-capped mangabeys (Cercocebus torquatus), collected from a total of 17 Individuals living in three different groups at the Station Biologique, Paimpont, France. When applying methods originally established in ape gesture research to assess whether these monkeys used ‘markers of intentionality’ during their gesture production, we found that 24 out of a total of 25 different signal types (including 4 facial expressions and 5 manual gestures) qualified as intentional. They were characterized by sensitivity to the attentional state of recipients, adjustment to audience effects, and goal persistence. Our results reveal that monkey communication is cognitively more complex than previously assumed, and show that the precursors to flexible and intentional communication were already present in the primate lineage around 30 My ago.