Purpose: Assessment of the effectiveness of dynamic contrast enhanced (CE-Dyn) T1-weighted and T2-weighted magnetic resonance imaging (MRI) sequences during the follow up of prostate carcinoma after external beam radiotherapy (EBRT) and to compare imaging findings with the pathological and transrectal ultrasound (TRUS) findings. Materials and Methods: In this retrospective study, MRI findings of 20 patients who had prostate carcinoma and treated by EBRT were evaluated to detect recurrence. MRI findings were compared with TRUS and pathological findings. Results: The sensitivity and specificity of TRUS, in detecting recurrent tumor after EBRT were 53.3 and 60%, respectively. In the same group, sensitivity and specificity of T2-weighted MRI were 86 and 100% respectively. On the other hand, the sensitivity and specificity of CE-Dyn T1-weighted series in diagnosis of the recurrent prostate cancer were 93% and 100% respectively. The accuracy of CE-Dyn T1-weighted images in the detection of recurrence was significantly higher as compare to T2-weighted images. Conclusion: During follow up of these patients, TRUS without using any other imaging or biochemical modality is not a sufficient method to detect recurrence. CE-Dyn T1-weighted MRI series increases the sensitivity of MRI in detecting recurrence in the follow up of prostate cancer after EBRT. CE-Dyn T1-weighted sequence must be a routine part of the protocol of MRI, during this patient’s follow up in terms of diagnosing the recurrence.