The present study aimed to clarify the inconsistent relationship between negative affect and innovative work behaviour by taking into account the role of affect activation and mindfulness. Building on the conservation of resources theory, we hypothesized that low-activated negative affect can be associated with increased innovativeness, but only for employees with high levels of mindfulness. Conversely, high-activated negative affect is expected to have a positive, direct relationship with innovative work behaviour. Data were collected from two independent samples, namely 163 French Canadian and 101 Italian employees. Consistent with our predictions, multiple regression analysis results showed that low-activated negative affect was positively related to innovative behaviour only when mindfulness was high (vs. low), whereas high-activated negative affect was directly associated with higher innovativeness. Our findings challenge the assumption that low-activated negative affects are associated with undermined innovative behaviour, suggesting that these affective states can be related to increased innovativeness if employees are mindful. On the other hand, they support the view that high-activated negative affects provide the energizing potential for instigating innovative actions. This study is unique in examining mindfulness as a moderator that is capable of shaping the link between deactivating negative affect and employee innovativeness. As such, it answers recent calls for research on how mindfulness can contribute to workplace functioning. Moreover, this is the first study to take into account the role of activation level in the negative affect-innovative work behaviour relationship.