Online shopping continues to simplify people's way of life in the present world. People no longer need to physically visit stores to buy items for home use or other purposes. This can be done online using mobile applications to order for preferred items, which can be delivered in return. However, the increase in the features of mobile applications and mobile devices makes usability testing a necessary aspect in today's advancement of technology. This paper uses an experiment-based usability testing evaluation on Lazada Indonesia mobile application to understand four usability factors, namely, ease of use, efficiency, functionality, and satisfaction. The test was performed using 40 participants and all were students from Universitas Atma Jaya Yogyakarta, Universitas Gadjah Mada, and Universitas Sanata Dharma. These performed 6 tasks on the mobile application and later answered a questionnaire to capture their views concerning the usability of the mobile application. The results were analyzed using SPSS software and descriptive statistics were displayed using standard deviation and arithmetic means. The results from the evaluation showed that the mobile application is easy to use, efficient, and has good functionality. However, some issues were mentioned by participants which indicated that users were not fully satisfied with the mobile application. Therefore, this calls for designers to consider these usability issues to increase user satisfaction.