Brachial plexus block is commonly used in shoulder surgery, as it provides satisfactory surgical conditions and adequate postoperative pain control. However, there are contradictory reports regarding the addition of tramadol to the injected regional anesthetic solution. We performed a prospective randomized study to evaluate the effectiveness of tramadol as an adjuvant to ropivacaine during interscalene brachial plexus block and assess its impact on the opioid consumption and the early postoperative pain in patients that underwent shoulder surgery. Eighty patients scheduled for elective shoulder surgery and anesthesia via interscalene brachial plexus block were randomly divided into two groups. In group A ( = 40), a solution of 40 mL of ropivacaine 0.5% and 2 mL (100 mg) of tramadol was administered during the brachial plexus block, while in group B ( = 40), a solution of 40 mL of ropivacaine 0.5% and 2 mL NaCl 0.9% (placebo) was administered. The effectiveness and duration of sensory and motor blocks were recorded in both groups. The sensory block was assessed recording the loss of sensation to pin prick test over the skin distribution of the axillary, radial, and musculocutaneous nerves. The motor block was assessed using the modified 3-point Bromage score (0-2 points). Cumulative morphine consumption and pain, using the Visual Analog Scale (VAS), were evaluated in both groups at 2, 4, 8, and 24 h after surgery. Sensory block onset was achieved earlier in group A than in group B (5.21 ± 3.15 minutes (min) vs. 7.1 ± 4.51 min, = 0.029). The motor block onset was similar between the two groups (13.08 ± 6.23 min vs. 13.28 ± 6.59 min; = 0.932). The duration of the sensory block was longer in group A as compared to group B (13 ± 2.3 h vs. 12 ± 2.8 h; = 0.013). The duration of the motor block did not present any difference between the groups (10 ± 2.2 h vs. 10 ± 2.8 h; = 0.308). Differences in morphine administration were not significant at 2, 4, and 8 h, however, morphine consumption was found to be decreased in group A 24 h postoperatively A ( = 0.04). The values of VAS were similar at 2, 4, and 8 h, however, they were lower in group A at 24 h ( < 0.013). Combined regional administration of tramadol and ropivacaine during interscalene brachial plexus block improves the time of onset and the duration of the sensory block, while it is associated with reduced morphine consumption during the first 24 h after shoulder surgery.