Aim This study aimed to compare the efficacy of bilateral infraorbital nerve block with Bupivacaine with intravenous Pentazocine for the control of immediate postoperative pain in children following cleft lip repair. Methods This was a randomized controlled clinical study conducted at the Department of Oral and Maxillofacial Surgery, Lagos University Teaching Hospital, Idi-Araba, Lagos. Participants were randomly allocated to either Group 1 to receive bilateral Infraorbital nerve block with 0.5% plain Bupivacaine (2 mg/kg) or Group 2 to receive intravenous Pentazocine (0.5 mg/kg) after cleft lip repair. The drugs were administered for immediately postoperative pain relief, just after the last suture was placed. Assessment of immediate postoperative pain was done using the FLACC (Face, Leg, Activity, Cry, Consolability) pain scale. Scoring was done at hourly intervals postoperatively, observing a child for 1 minute at each hour. When a child’s pain score exceeded 3 on the FLACC pain scale rescue analgesia with intravenous Paracetamol (20 mg/kg) was administered in the two group. The duration of postoperative analgesia was noted as the time from administration of the intervention to the time rescue analgesia was administered. The study was concluded for each participant at the demand for rescue analgesia. Data collection was done using a proforma and analysis performed using IBM SPSS Statistics for Windows (version 21.0, IBM Corp., Chicago, IL, USA). For all comparisons p<0.05 was adopted as the criterion for establishing a statistical significance. Results Forty participants who satisfied the inclusion criteria were enrolled in the study (20 in each study group). Both groups were comparable for age, sex, weight and duration of surgery. The mean duration of analgesia in the bilateral Bupivacaine infraorbital nerve block group was longer (291.80 ± 95.4 minutes) than that of the intravenous Pentazocine group (151.50 ± 24.9 minutes). This difference was statistically significant (p=0.001). By the 3rd hour post-surgery, a significant number (N=15, 75%) of participants in the Pentazocine group received rescue analgesia, while only 2 (10%) participants in the Bupivacaine group received rescue analgesia at the same time point. The FLACC pain score remained low throughout the period during which both drugs were effective, however, at zero, 1st, 3rd, and 5th hour the FLACC pain scores in the Pentazocine group were lower than those in the Bupivacaine group and these differences were statistically significant (p=0.044, p=0.011, p=0.020 and 0.023, respectively).