Test anxiety is a serious problem for many college students. This study examines the development and validation of the Online Test Anxiety Inventory (OTAI) to evaluate test anxiety among online students. In this study, the OTAI is developed and administered to a sample of 157 postgraduate online students: 77 males and 80 females, aged 22 to 51 years. To design the initial version of the 38-item, Sarason's Test Anxiety Scale, Abolghsemi's Test Anxiety Inventory (TAI) and Spielberger's Test Anxiety Scale were studied, and many interviews were conducted with online learning students who had a high level of test anxiety. Confirmatory Factor Analysis was employed to obtain the Goodness of Fit Indices of the model to the data. The final result is a multidimensional, 18-item OTAI comprised of three factors--online, psychological, and physiological--with a high internal consistency (a = 0.91) and acceptable criterion validity. Concurrent validity was measured by the association of the OTAI and the TAI (r = 0.83).