Ecological momentary assessment (EMA), or the repeated assessment of individuals' behaviors and experiences over time, is a methodologically advantageous approach to the study of psychological constructs. Recently, advances in computer technology have allowed for EMA research to be conducted in a more convenient, automated, and secure manner by administering surveys on participants' telephones and storing the results directly to a central server. The present article introduces TelEMA, an easy-to-use, low-cost telephone assessment platform for clinical and research applications. A single server running TelEMA can be shared among many experimenters, studies, and participants simultaneously. TelEMA routes telephone calls and text messages through a third-party service, so experimenters may conduct studies with no up-front cost or technical expertise. TelEMA provides a secure Web interface for experimenters or clinicians to design studies, enroll participants, monitor compliance, and collate response data from anywhere. Participants complete surveys using their own telephones. Surveys may contain keypress or voice recording questions, and the timing and content of each survey may be randomized and customized. A pilot study was conducted in which individuals used the TelEMA system to complete four randomly timed surveys per day for one week; the surveys assessed state affect and social anxiety. Results indicated that participants found TelEMA easy to use and secure, and compliance rates were on par with other EMA methods using mobile devices. Overall, TelEMA is a practical and robust system that enables fast and inexpensive deployment of EMAs.