Chronic exposure to stressors is associated with the emergence of psychiatric disorders, but the underlying mechanisms are unclear. We previously showed that developmental chronic unpredictable stress (CUS) diminishes the habituation of dorsal raphe nucleus (DRN) serotonergic (5-HT) neurons to acute stressors and enhances anxiety-like responses. Here, we investigated whether the change in 5-HT DRN habitution underlies CUS-induced behavioural alterations. We exposed larval zebrafish to the CUS, subsequently ablated DRN 5-HT neurons using chemogenetics and assessed different types of anxiety-like and social behaviors. We found that CUS has a generic facilitating effect on anxiety and delays the habituation to a novel environment. Ablation of the DRN does not rescue the entire CUS-induced anxiety-like phenotype, but improves habituation to novelty following CUS exposure.Whole-brain neural activity maps and sensory habituation assays are currently beeing conducted to further characterize the consequences of the impaired and the intact habituation capacity of the DRN following CUS. We conclude that CUS exposure impairs 5-HT DRN habituation, which in turns alters specific aspects of the anxiety-like phenotype that involve habituation to a novel environment.