Background: Common cold is the most common disease which mainly affects the upper respiratory system. It is caused by viral or, in a small percentage, by bacterial infections. Current therapy options focus on symptomatic relief of the disease such as nasal saline irrigation, an easy-to-apply, comfortable, non-toxic method. In this study, a novel hypertonic seawater solution enriched with hyaluronic acids, eucalyptus oil, copper and manganese salts, Stérimar Stop & Protect Cold and Flu (SSPCF), has been investigated with respect to efficacy against viral and microbial infections. Methodology: An in vitro 3D reconstituted human nasal epithelium tissue model, MucilAir™, has been used in this study. Pretreatment and post-treatment anti-viral effects of SSPCF was measured through HRV-A16 viral load assays in order to evaluate the preventive and therapeutic efficacy of SSPCF, respectively. Anti-bacterial effects of SSPCF was assessed via Staphylococcus (S.) aureus growth inhibition and fluorescence bead-based phagocytosis assays. Results: One-hour SSPCF treatment pre-or post-viral infection inhibited the viral replication up to 99.78 and 59.91%, respectively. S. aureus growth was completely eliminated (100%) in SSPCF treated tissues after 1 hour of treatment. Phagocytosis rate was 3.28 folds higher in SSPCF treated tissue as compared to saline treated controls. Conclusions: Under the conditions of this in vitro study, SSPCF appears effective against some species of rhinoviruses (as in common cold) and S. aureus in vitro.