This study aims to explore usability issues of watch‐type wearable devices and to suggest guidelines for improved operation of smartwatches. To do so, we conducted a series of surveys, interviews, and task performance experiments. Thirty smartwatch users from ages 20 to 43 years were recruited. Users’ experiences of smartwatches were collected via a weeklong, online‐based diary study, which consisted of various tasks to be completed while smartwatches were in use. Our study assessed usability problems associated with those tasks, concurrent tasks conducted while interacting with smartwatches, pain points/discomfort that users had while interacting with their devices, and requirements/requests of the smartwatch users. During the week of tracking, participants were asked to complete the usability evaluation three times a day using usability principles we designed for the study: information display, control, learnability, interoperability, and preference. In addition, task performance tests were conducted for the tasks most frequently conducted on touch‐based displays: number entry, swiping, and scrolling. Specific usability issues of smartwatches were identified and summarized for each usability principle by triangulating survey, interview, and task performance evaluation results. Based on the insights from the results of the study, we conclude by suggesting guidelines for further enhancing users’ experience of future smartwatches.