The concept of demotivation and removing possible barriers of learning has been researched and advocated throughout the ESL/EFL literature but it seems that it has not been well studied at least on Iranian seminary EFL learners. As such, this study aimed at investigating the effect of demotivation on oral performance of Iranian EFL seminary learners and finding possible demotivating factors which may affect it. The participants were 50 male intermediate EFL learners studying at Islamic Propagation Office, Isfahan, Iran, selected based on their performance on the Oxford Placement test. A pretest-posttest design oral performance exam was used. The participants were divided into two groups of motivated and demotivated group based on the motivational questionnaire (Celce-Murcia, Brinton, & Goodwin, (1996). The collected data included: (1) the results of the motivational questionnaire, (2) the results of the oral tasks (used as pre and post tests) and (3) responses to a semi-structured interview regarding the possible demotivating factors which may influence participants' oral performance. The independent sample t-test and paired samples t-test were used to determine whether there were significant inter and intra-group differences. The results provide evidence that motivation helps enhance EFL seminary learners’ oral performance and demotivation significantly hinders improving it.