The present disclosure pertains to a method and system configured for detecting a gas delivery malfunction in a spontaneous mechanical ventilation mode. In some embodiments, the system comprises a pressure generator, a subject interface, one or more sensors, one or more processors, electronic storage, a user interface, and/or other components. The detection of a gas delivery malfunction in a spontaneous mechanical ventilation mode is implemented by generating a test flow of gas for delivery to an airway of a subject, and monitoring a responsive flow of gas in the subject interface. If one or more parameters associated with the responsive flow of gas demonstrate inconsistencies with a reference flow of gas responsive to the test flow under a condition that there is no gas delivery malfunction, the system determines that there is a gas delivery malfunction.