Analgesic effects of the above two block modalities in this procedure are still unclear. This study aimed to compare the analgesic efficacy of pericapsular nerve group block (PENG) and Fascial iliaca compartment block (FICB) in proximal femoral nailing anti-rotation in elderly patients. This study retrospectively analyzed the clinical data of 80 elderly patients who underwent anti-rotational proximal femoral nailing after trochanteric fracture from May 2023 to March 2024. The researchers were divided into two groups: PENG group and FICB group with 40 cases in each group. Changes in relevant indexes before nerve block (T0), 10 min after block (T1), 20 min after block (T2), at the time of over-bed placement (T3), 24 h after surgery (T4), and 48 h after surgery (T5) were recorded and compared between both groups. The visual analog scale (VAS) scores of T3 and T4 in the PENG group were 4 (3, 5) and 3 (2, 3), respectively, which were significantly lower than those of 5 (4, 6) and 3 (3, 4) in the FICB group (p < 0.05). Mean arterial pressure (MAP) and heart rhythm (HR) at T3 in the PENG group were significantly lower than in the FICB group (p < 0.05). The cumulative intraoperative and postoperative remifentanil dosage in the PENG group (443.58 ± 78.88 µg) was less than the FICB group (487.43 ± 79.72 µg) (t = 2.473, p = 0.016). PENG group had significantly higher Lovett muscle strength scores at T4 and T5 (p < 0.05). Postoperative complications incidence did not differ significantly between both groups (p > 0.05). Analgesic effect of PENG block on anti-rotation of the proximal femoral nail is superior to that of FICB in elderly patients. There was less opioid accrual before and after the procedure, less impact on lower extremity muscle strength, and no significant adverse effects.