Background Temporomandibular disorder (TMD) is a group of disease which affects the temporomandibular joint (TMJ) and supporting tissues of the musculoskeletal structures. Arthrocentesis is an effective treatment modality for TMD, especially in patients who suffer from pain and limited mouth opening. Objective The aim of this study was to investigate the effects of pre-operative and intra-operative variables on the clinical outcome of arthrocentesis therapy. Methods The records of 83 patients diagnosed as disc displacement (DD) without reduction according to DC/TMD, and treated with arthrocentesis were selected. Sex, age, bruxism history, pain intensity and maximum mouth opening (MMO) were recorded as pre-operative variables. Extravasation and the amount of irrigation were recorded as intra-operative variables. The success of the arthrocentesis procedure was determined as MMO <35 mm and pain intensity lower than 3, at third-month follow-up. Results At 3-month follow-up, clinical evaluation showed a significant reduction in TMJ pain and an increase in MMO (P < 0.05). It was found that patients with an unsuccessful outcome are those who had a more restricted MMO and severe pain before the procedure. Extravasation was found to be a significant factor that affects the success of the procedure. Conclusion The success of arthrocentesis in TMJ DD without reduction is adversely affected by the severity of the pre-operative clinical symptoms. Extravasation is also a factor that has a negative effect on the success of the procedure.