Objectives. The aim of this study was to determine the effectiveness of preoperative administration of single-dose of paracetamol-codeine, in the relieving of acute postoperative pain after the surgical removal of an impacted mandibular third molar. Materials and Methods. The study cohort consisted of 32 Caucasian outpatients, giving a total of 64 bilateral symmetrical impacted mandibles. Patients were randomized in two experimental groups to receive a preoperative oral dose of paracetamol-codeine (analgesic group) or a placebo (placebo group) at the first and second surgeries. Study participants were asked to record pain intensity scores during the operation and the next 2 days, the time of the first request for rescue analgesic, and the total number of postoperative-supplement paracetamol-codeine tablets. Results. The pain intensity score on the first day was significantly lower in the analgesic group than in the placebo group (p < 0.001). The time to using rescue therapy was significantly longer in the analgesic group than in the placebo group (p = 0.004). The number of paracetamol-codeine tablets used postoperatively did not differ between the analgesic and placebo groups (p = 0.104). Conclusions. Preoperative paracetamol-codeine is effective in providing immediate postoperative pain control after third molar surgery and in delaying the initial onset of pain. This trial is registered with ClinicalTrials.gov Identifier (Registration Number): NCT03049878.