Background Assessment of maximum respiratory pressures is a common practice in intensive care because it can predict the success of weaning from ventilation. However, the reliability of measurements through an intubation catheter has not been compared with standard measurements. The aim of this study was to compare maximum respiratory pressures measured through an intubation catheter with the same measurements using a standard mouthpiece in extubated patients. Methods A prospective observational study was carried out in adults who had been under ventilation for at least 24 h and for whom extubation was planned. Maximal respiratory pressure measurements were carried out before and 24 h following extubation. Results Ninety patients were included in the analyses (median age: 61.5 years, median SAPS2 score: 42.5 and median duration of ventilation: 7 days). Maximum respiratory pressures measured through the intubation catheter were as reliable as measurements through a standard mouthpiece (difference in maximal inspiratory pressure: mean bias = − 2.43 ± 14.43 cmH2O and difference in maximal expiratory pressure: mean bias = 1.54 ± 23.2 cmH2O). Conclusion Maximum respiratory pressures measured through an intubation catheter were reliable and similar to standard measures. Clinical trial registration Retrospectively Registered in ClinicalTrials.gov (NCT02363231).