Objective: In this study, the aim was to investigate the effect of hyoscine N-butylbromide (HnBB) pretreatment on pain during propofol injection. Subjects and Methods: In this prospective, randomized, placebo-controlled and double-blind trial, 60 patients scheduled to undergo routine outpatient surgery under general anesthesia were randomly allocated to 2 groups, the HnBB (n = 30) and sodium chloride (n = 30) groups. Twenty seconds after the injection of 20 mg HnBB or 0.9 % sodium chloride, a 50-mg dose of propofol was injected in 2-3 s. Ten seconds later, the pain intensity was assessed using a 4-point scale: no pain (0), mild (1), moderate (2), and severe (3) pain. The Student t test was used for the analysis of parametric data and the Pearson χ2 test for categorical data. Results: The occurrence of pain in the HnBB group (43.3%) was significantly lower than the control group (73.3%) (p < 0.018). Of the 30 patients in each group, 10 in the control group and 3 in the HnBB group experienced severe pain (p = 0.001). Conclusions: Pretreatment with 20 mg HnBB significantly reduced propofol injection pain compared to placebo.