Objective <p>To assess the effectiveness of an intervention programme combining Oropharyngeal Myofunctional Therapy (OMT) and cervical spine exercises in the general population with mild to moderate Obstructive Sleep Apnoea (OSA), analysing its impact on respiratory variables (AHI, MSatO₂, ODI, TC90, Supine AHI), daytime sleepiness and quality of life.</p> Materials and methods <p>A single-blind randomised clinical trial with 32 participants diagnosed with mild to moderate OSA, assigned into two groups: control (<i>n</i> = 16) and intervention (<i>n</i> = 16). Both groups received hygiene- and diet-related recommendations, and the intervention group completed an OMT programme and cervical spine exercises over 20 weeks (May 2023–November 2024). The respiratory variables were evaluated using respiratory polygraphy, and daytime sleepiness and quality of life were measured using the Epworth Sleepiness Scale and EuroQol-5D scales, respectively.</p> Results <p>No statistically significant differences were found between groups (Median [IQR]): Apnoea–hypopnoea index (2.0 [-6/6], CI 95%, <i>p</i> = 0.86), Mean oxygen saturation (-0.5 [-1/0], CI 95%, <i>p</i> = 0.43), Oxygen Desaturation index (1.0 [-1/5], CI 95%, <i>p</i> = 0.72), Time with oxygen saturation below 90% (1.0 [0/3], CI 95%, <i>p</i> = 0.10), Epworth Sleepiness Scale score (-1.5 [-4/0], CI 95%, <i>p</i> = 0.83), and EuroQol-5D quality of life questionnaire (5.0 [0–10], CI 95% <i>p</i> = 0.08).</p> Conclusion <p>The comprehensive 20-week OMT programme and cervical spine exercises showed no effectiveness in improving respiratory parameters, daytime sleepiness or quality of life in patients with mild to moderate OSA compared to hygiene- and diet-related measures alone. The null results observed in this study suggest relevant clinical implications, such as the limited efficacy of low-frequency OMT protocols.</p>