Experimental evidence suggests that environmental stress conditions can alter the expression of BDNF and the levels of this neurotrophin influence the behavioural response in mammalian models. Recently it has been demonstrated that the exposure to 34° C for 21 days alters the brain proteome and behaviour in zebrafish. The aim of this work was to investigate the role of BDNF in the nervous system of adult zebrafish under control and heat treatment conditions. For this purpose, wild type (WT), heterozygous BDNF+/- (HT) and knock out BDNF-/- (KO) zebrafish were kept for 21 days at 26° C or 34° C and then euthanized for brain analysis or subjected to behavioural tests (Y-maze test, novel tank test, light and dark test, social preference test, mirror biting test) used for assessing behavioural aspects such as boldness, anxiety, social preference, aggressivity, interest for the novel environment and exploration. RTqPCR analysis showed the reduction of gene expression of BDNF and its receptors after heat treatment. Moreover, proteomic analysis and behavioural tests showed genotype- and temperature-dependent effects on brain proteome and behaviour of zebrafish.