The growth hormone secretagogue receptor (GHSR) is a G-protein coupled receptor highly expressed in the brain that modulates a variety of metabolic, endocrine, autonomic and behavioural functions. GHSR is activated by ghrelin and blocked by a liver-derived hormone named Liver-expressed antimicrobial peptide 2 (LEAP2). Here, we developed a novel fluorescent GHSR ligand based on the N-terminal sequence of LEAP2, hereafter called FLEAP2, and assessed its capability to label GHSR in the mouse brain. We found that FLEAP2 impaired ghrelin-induced food intake in the same fashion that native LEAP2 when administrated intracerebroventricularly (ICV) in mice. Furthermore, in mice ICV-injected with FLEAP2, we found that brain regions with the highest fluorescent signal were the CA3 region of the hippocampus and the arcuate nucleus of the hypothalamus. In order to test the specificity of FLEAP2 towards GHSR labelling, we ICV injected mice with FLEAP2 after ICV pre-treatment with vehicle, native LEAP2 or ghrelin. We analysed the level of fluorescent signal in the arcuate nucleus of these mice, as it is the brain region with highest GHSR expression, and mice pretreated with native LEAP2 or ghrelin had lower fluorescent signal than vehicle pretreated mice. Thus, current data indicate that FLEAP2 specifically binds to GHSR and is an appropriate tool to study LEAP2 binding and function in the mouse brain.