Mouth breathing during sleep is commonly observed in patients with obstructive sleep apnea (OSA) and is associated with increased upper airway collapsibility. Studies suggest that mouth breathing alters upper airway anatomy and aerodynamics, potentially worsening OSA severity. Research on mouth taping as a therapeutic approach for OSA has shown mixed results. Some studies report reduced apnea–hypopnea index (AHI) and improved inspiratory flow in selected patients, while others suggest that mouth taping may exacerbate symptoms in individuals with velopharyngeal obstruction. Oral appliances like mouth tape and shields have demonstrated potential in improving continuous positive airway pressure compliance and also reducing OSA severity. However, patient selection is crucial, as mouth taping may not be suitable for obese individuals or those with severe OSA based on current understanding. Treating nasal obstruction and pre-treatment drug-induced sleep endoscopy (DISE) are recommended to identify suitable candidates.