Cystic fibrosis (CF) patients are at risk of acquiring chronic Pseudomonas aeruginosa lung infections. The biofilm mode of growth of P. aeruginosa induces tolerance to antibiotics and the host response; accordingly, treatment failure occurs. Supplemental azithromycin has proven beneficial in CF owing to potential immunomodulatory mechanisms. Clinical studies have demonstrated a reduction in exacerbations in CF patients by avian IgY anti-Pseudomonas immunotherapy. We hypothesise that azithromycin pre-treatment could potentiate the observed anti-Pseudomonas effect of IgY opsonisation in vivo. Evaluation of phagocytic cell capacity was performed using in vitro exposure of azithromycin pre-treated human polymorphonuclear neutrophils to IgY opsonised P. aeruginosa PAO3. A murine lung infection model using nasal planktonic P. aeruginosa inoculation and successive evaluation 24 h post-infection was used to determine lung bacteriology and subsequent pulmonary inflammation. Combined azithromycin treatment and IgY opsonisation significantly increased bacterial killing compared with the two single-treated groups and controls. In vivo, significantly increased bacterial pulmonary elimination was revealed by combining azithromycin and IgY. A reduction in the inflammatory markers mobiliser granulocyte colony-stimulating factor (G-CSF), macrophage inflammatory protein 2 (MIP-2) and interleukin 1 beta (IL-1β) paralleled this effect. Combination of azithromycin and anti-Pseudomonas IgY potentiated the killing and pulmonary elimination of P. aeruginosa in vitro and in vivo. The augmented effect of combinatory treatment with azithromycin and IgY constitutes a potential clinical application for improving anti-Pseudomonas strategies.