In contrast to human adults, risk proneness in the gain domain is usually observed in both young children and non-human primates. It is currently unclear what mechanism might be underlying such economic preferences. We investigated decision-making under risk of gain in toddlers and monkeys. The choices of 2.5-year-old children and red-capped mangabeys (Cercocebus torquatus torquatus) were examined in a gambling task for food reward in which participants have to choose between two options, a secure option and a risky option. In contrast to monkeys, toddlers showed a strong preference for the risky option over the safe option. In order to test the hypothesis that risky choices in participants reflect inhibitory control difficulties, toddlers and mangabeys were presented in Experiment 2 with a situation analogous to that used in Experiment 1 except for the fact that the opaque cover under which was placed the secure option was replaced by a transparent cover. In this second experiment, toddlers continued to show a preference for the risky option over the safe option. In contrast, mangabeys showed a preference for the safe option over the risky option in Trial 1 but they shifted their economic preferences in Trial 2. We argue that decision-making strategies under risk of gain in both toddlers and mangabeys (a) do not reflect poor behavioral control and (b) are not reducible to perception-action couplings.