Background: Several researchers have suggested that addition of local anesthetics to spinal anesthesia increases the duration of postoperative analgesia. Objectives: This study sought to assess the effect of addition of clonidine to bupivacaine in spinal anesthesia on analgesia after cruciate ligament repair. Patients and Methods: This double-blind clinical trial was conducted on 50 American Society of Anesthesiologists (ASA) class I or II patients who were candidates for cruciate ligament repair. Patients were randomly assigned to two groups; one group received 15 mg of bupivacaine (group B) and the other 15 mg of bupivacaine plus clonidine (75 µg, group BC). The two groups were compared in terms of post-operative analgesia and related factors using the SPSS software version 20. Results: All patients were males with a mean age of 24.9 years in group B, and 25.2 years in group BC (P > 0.05). In group BC, time lapse to request analgesics was 160 minutes longer and the Visual Analog Scale (VAS) at this time was 0.3 units less than group B. The time to regression of sensory block by two dermatomes was seven minutes longer, VAS in the recovery room was 1 unit less and Bromage scale in the recovery room and ward was 0.6 and 0.9 units more, respectively in the BC group. Hypotension and ephedrine usage was 36% more in the BC group (P < 0.05). Conclusions: Clonidine plus bupivacaine can increase the duration of motor and sensory block in arthroscopic cruciate ligament repair under spinal anesthesia. However, due to significant hemodynamic changes, further studies are required to determine a safer dose.