Nasal administration of drugs is the first choice in the treatment of acute and chronic nasal mucosa disorders such as rhinitis and rhinosinusitis with or without polyps. The efficacy of nasally administered drugs is dependent on the physiology of the nasal mucosa and the physiochemical properties of the drug and formulation. Current research is focused on the development of innovative drug delivery nanosystems which ensure prolonged residence time at the nasal mucosa and improve the pharmacokinetic profile, thereby improving efficiency and safety of nasal drug administration. The aim of this work was to prepare dexamethasone-loaded lipid/alginate nanoparticles, determine their physiochemical properties and biocompatibility in vitro. In biocompatibility studies, Caco-2 cell line, originally derived from a colon carcinoma, were used as the model epithelial cells. Lipid/alginate nanoparticles were successfully prepared by ionic interaction between anionic polymer alginate and positively charged lipid mixture (lecithin and cationic lipid dimethyl-dioctadecyl-ammonium bromide (DDAB)). Nanoparticles with different amounts of DDAB were prepared. The size of dexamethasone-loaded lipid/alginate nanoparticles was in range from 109.1 to 258.6 nm, and the surface charge was from -14.2 to -31.7 mV. For all prepared nanoparticles, dexamethasone entrapment efficiency was higher than 50 %. Entrapment of dexamethasone did not significantly affect the size or the surface charge of nanoparticles. All nanoparticles were characterized by prolonged dexamethasone release. Among the developed nanoparticles, nanoparticles with the highest amount of DDAB (lecithin: DDAB 10:1) had the best physiochemical properties: they were characterized by the highest entrapment of dexamethasone (entrapment efficacy was 63.8 %, and the content of dexamethasone in the suspension of nanoparticles 255 ± 7 μg/ml), the most negative zeta potential (-31.7 mV), the appropriate size (252.3 nm) and the lowest polydispersity index (0.241). The biocompatibility of nanoparticles was determined by monitoring the metabolic activity of Caco-2 cells after a two-hour exposure to different concentrations of nanoparticle suspensions (50, 100, 200, 400 μg/ml). The viability of Caco-2 cells was not significantly changed after exposure to suspensions of nanoparticles in the tested concentration range and duration, which demonstrates their potential for safe nasal administration of dexamethasone.