A large number of patients suffering from asthma or chronic obstructive pulmonary disease (COPD) can show overlapping features of both diseases. Several subjects affected by asthma-COPD overlap (ACO) may be at a severe stage, poorly responsive to triple therapy including inhaled corticosteroids, long-acting β2 agonists and muscarinic antagonists. This review tries to explore whether omalizumab can be used in poorly controlled severe ACO patients. According to the few studies available, omalizumab may improve asthma outcomes in ACO, although the magnitude of improvements may be lower in comparison to those obtained in subjects affected only by severe asthma. Omalizumab, by acting on IgE, might improve the eosinophilic pattern which is characteristic of the ACO asthma inflammation component. It can be hypothesized that a prevalence of Th1/Th17 airway inflammation pathways can modulate a lower response to anti-IgE while a Th2 pattern can lead to a higher effectiveness to omalizumab in ACO. High levels of IgE, FeNO and blood eosinophil count may be markers of a better response to omalizumab. In conclusion, on the basis of the few studies available, omalizumab could be effective in poorly-controlled severe ACO, although to a reduced extent in comparison to patients affected only by asthma.