In this study, we suggest the development of nanoparticle loaded in situ gelling system suitable for corticosteroid nasal delivery. We propose lipid/alginate nanoparticles (size 252.3 ± 2.4 nm, polydispersity index 0.241, zeta-potential −31.7 ± 1.0 mV, dexamethasone (Dex) content 255 ± 7 μg ml−1) dispersed in pectin solution (5 mg ml−1) that undergoes a sol-gel phase transition triggered by Ca2+ present in nasal mucosa. The viscoelasticity of gel obtained by mixing nanoparticle suspension in pectin continuous phase with simulated nasal fluid (1:1 V/V) is characterised by a log-linear shear thinning viscosity behaviour. Observed viscosity corresponds to the range of viscosities of nasal mucus at physiological as well as under disease conditions. Nanoparticle-loaded gel was biocompatible with the selected epithelial cell model and, in comparison to dexamethasone solution, provided reduction in Dex release (t50% 2.1 h and 0.6 h, respectively) and moderated transepithelial permeation in vitro (Papp 7.88 ± 0.15 and 9.73 ± 0.57 × 10−6 cm s−1, respectively). In conclusion, this study showed the potential of the proposed system to provide local therapeutic effect upon administration of a lower corticosteroid dose and minimize the possibility for adverse effects as it can be easily sprayed as solution and delivered beyond nasal valve, ensure prolonged contact time with nasal mucosa upon gelation, and moderate corticosteroid release and permeation.