Purpose: To assess the analgesia and side effects of codeine phosphate associated with paracetamol (test medication) as compared to paracetamol (control medication) after the extraction of impacted mandibular third molars. Materials and methods: Forty-seven patients removed the right and left impacted mandibular third molars. After one surgery, patients took the test medication and after the other surgery, they took the control medication. Patients with exacerbated pain were prescribed to use the rescue medication instead of the medication initially administered and were included in the rescue group. They were evaluated for 7 days postoperatively, and the mean score of the visual analogue scale (VAS) of pain between test and control medications was assessed by the Poisson distribution. The side effects of these medications were assessed by the patient's complaints. A P value of < .05 was considered to be statistically significant. Results: The mean score of the VAS of pain was not statistically different between test and control medications in the non-rescue group, but it was significantly greater in patients previously using paracetamol in the rescue group. The most common side effects reported in both groups, predominantly in patients using the test medication, were drowsiness, dizziness, and nausea. Conclusion: The use of codeine phosphate associated with paracetamol after the extraction of impacted mandibular third molars is a better choice to control the postoperative pain rather than paracetamol, but with more side effects, which are clinically acceptable.