Cooperation is thought to be a necessary condition to solve collective dilemmas such as climate change or the sustainable use of common-pool resources. Yet, it is poorly understood how situations pervaded by thresholds shape the behaviour of people facing collective dilemmas. Here we provide empirical evidence that resource users facing thresholds maintain on average cooperative behaviours by maximising their individual earnings while ensuring future group opportunities. A dynamic game with 256 Colombian fishers helped us investigate behavioural responses to the existence of thresholds, risk and uncertainty. Uncertain thresholds made fishers maintain higher levels of cooperation than when the risk of thresholds is known, but risk had a stronger effect on reducing individual fishing effort. If cooperation increases in the face of thresholds, then communicating uncertainty is more policy-relevant than estimating precisely where tipping points lay in social-ecological systems.