Nasal drug administration is the first choice for the treatment of topical nasal disorders, however it represents an alternative route to classic administration routes with the aim to reach the systemic circulation of the drug. In situ gelling systems represent suitable nasal drug delivery platform. They can be formulated in solutions or suspensions that gel at the site of administration due to change in pH, temperature or due to the presence of ions. Low viscosity of in situ gelling systems enables simple administration by spraying, while viscoelastic gel properties ensures prolonged retention at the site of administration and consequent improved therapeutic effect and/or improved drug absorption. The aim of this study is to evaluate the applicability of gum gel in the preparation of an in situ gelling system for nasal drug administration. Melatonin was chosen as the model drug. It is commonly used in the treatment of insomnia, prevention and reduction of the jet lag symptoms, and circadian rhythm regulation. It is commonly administered orally resulting in low and variable bioavailability, therefore nasal administration of melatonin represents an alternative route of administration with the potential to improve its bioavailability. In this study, gellan gum based (0.6 %, 0.4 % and 0.2 %; m/m) in situ gelling systems with mannitol (4 %, m/m) as an isotonizing agent and melatonin (0.05 %, m/m) as a model drug, have been prepared. Viscosity of the in situ gelling systems was approximately equal to the viscosity of the purified water at the standard nasal spray shear rates. Gelation of the in situ gelling systems occurred soon after mixing with simulated nasal fluid. Gel strength increased with increasing gellan gum concentration in in situ gelling systems. Influence of the encorporation of the model drug on the gellation time and gel strength was shown to be dependent on the gellan gum concentration. Prolonged melatonin release profile was observed for all the formulations, however, there was no significant difference in the melatonin release rate from the in situ gels differing in gellan gum concentration, indicating very porous tridimensional structure of the gel formed. Conclusively, gellan gum is a suitable constituent of nasal in situ gelling systems. At concentrations above 0.2 % (m/m) it can provide in situ gellation after spraying in the nasal cavity. The addition of gellan gum at concentration below 0.2 % (m/m) can be considered with the aim to optimize the rheological properties of the system based on at least one other component with the in situ gelling ability.