Background: A major impediment to the provision of obstructive sleep apnoea (OSA) treatment is reliance on labour-intensive and costly laboratory-based polysomnography (PSG). Aims: To investigate if measurement of oximetry and nasal flow through the ApneaLink device (AL) could identify patients with moderate–severe OSA among those referred for PSG to a tertiary sleep service. Methods: New referrals to The Prince Charles Hospital Sleep Disorders Centre were assessed for suitability. Demographics, anthropometrics, Epworth Sleepiness and OSA50 scores were collected. Exclusion criteria included age <18 years, pregnancy, significant cognitive impairment, poorly controlled psychiatric disorder, domiciliary oxygen and prior OSA treatment. Participants underwent concurrent type 1 PSG and AL assessments. Results: One hundred participants had a mean age of 55 years (standard deviation 17) and were 49% male. Forty-eight (48%) had moderate–severe OSA on PSG. Composite variable AL 3% oxygen desaturation index ≥16 and AL apnoea–hypopnoea index (AHI) ≥15 had receiver operator characteristic area under the curve of 0.87, sensitivity of 80% and specificity of 94% for PSG AHI ≥15. The three false-positives seen with this composite variable had PSG AHI 11–14 and Epworth Sleepiness Score 6–17. The various composites of AL, anthropometric and questionnaire variables did not improve the AUC or specificity but did improve sensitivity. Conclusions: AL is useful in the diagnosis of moderate–severe OSA in patients referred to a tertiary sleep disorders centre. This could lessen reliance on PSG, expedite OSA care, lead to significant cost savings and make diagnosis of OSA more available in non-urban areas.