This paper proposes MonDep, a web-mobile application for the monitoring of patients with mild and moderate depression based on the PHQ-9 test and the automatic evaluation of therapeutic diary entries. MonDep allows patients to record their daily activities in a therapeutic diary, which is evaluated using sentiment analysis and their results of the PHQ-9 test. This allows the specialist to monitor the progress of the patient's depression treatment through a dashboard. The usability test applied to three depression psychologists shows that they find it user-friendly and easy to access. Due to its usability, low cost, and reliability, this application will be useful for the treatment of depression and will reduce treatment discontinuation.