The frequency and features of errors that occur during the handling of inhaler devices have been studied worldwide. However, such data are lacking in Japan. Thus, we examined the frequency and features of inhaler handling errors in patients with asthma in clinical practice in Japan. At least one error for Ellipta®, Discus®, Turbuhaler®, pressurized metered dose inhalers, and soft mist inhalers was observed at the rate of 25.7%, 50.0%, 57.7%, 68.4%, and 71.4%, respectively (p = 0.0005). On the other hand, asthma control test scores did not correlate with critical handling errors (p = 0.11) or the number of inhaler handling errors (p = 0.073). Inhalation errors were common and varied widely among the different inhaler devices in Japan. In the future, it is necessary to develop specific instructions based on the features of each device in order to improve inhalation technique and asthma control.