Introduction Chest impedance (CI) is the current standard for cardio-respiratory monitoring in preterm infants but fails to provide direct and quantitative information on diaphragmatic activity. Transcutaneous electromyography (dEMG) is able to measure diaphragmatic activity, but its feasibility and repeatability to monitor respiratory rate (RR) and heart rate (HR) in preterm infants needs to be established. Methods RR and HR were measured simultaneously by dEMG and CI for 1–hour on day 1, 3, and 7 of life in 31 preterm infants (gestational age 29.6 ± 1.8 weeks; birth weight 1380 ± 350 g) on non-invasive respiratory support. Six fixed 1-minute time intervals were selected from each 1-hour recording and both RR and HR were calculated using all intervals or only those with stable dEMG and CI recordings. Results dEMG was well tolerated and signal quality was good. Both RR and HR measured by dEMG and CI were significantly correlated (RR: r = 0.85, HR: r = 0.98) and showed good agreement by the Bland–Altman plot (mean difference (limits of agreement): RR: −2.3 (−17.3 to 12.7) breaths/min and HR: −0.3 (−5.3 to 4.7) beats/min. When analyzing only stable recordings, the correlation (r = 0.92) and agreement (−1.8 (−12.3 to 8.7) breaths/min) for RR improved. Subgroup analyses for postnatal age, gestational age, and mode of support showed similar results suggesting good repeatability of dEMG. Conclusion This study shows that monitoring RR and HR with transcutaneous dEMG is feasible and repeatable in preterm infants.