The physical form of the drug dictionary has many shortcomings, one of which is thick, impractical and it takes a long time to search for the drug terms. This is the motivation for the development of a drug dictionary application, namely the drug e-dictionary. The drug e-dictionary that was developed in 2019 has not been tested for usability. Usability testing is very important for applications that have been developed because it is the key to the success and requirements of user acceptance of the application. This study aims to test the usability of drug e-dictionary. The usability testing method used is the Retrospective Think-Aloud Method and the USE Questionnaire. The results of the first usability test provide some suggestions in the form of adding an autocomplete feature, query suggestion to the search function. Also, other suggestions are in the form of a display interface and page functions on the A-Z drug index. After making improvements according to the suggestions, the second usability test is carried out. The results of the second usability test showed an increase in the usability value from 75% to 86%. This shows that the input from respondents from the results of the first test can improve the quality of the drug e-dictionary application so that the application can be accepted by users.