Background: This study evaluated whether IMRT using fewer beams and segments could reduce delivery time without compromising plan quality in gastric cancer adjuvant radiotherapy. Materials and Methods: Fifteen patients with advanced gastric cancer who underwent D2, R0 surgery were included in this study. IMRT plans for each patient were designed as 7 equal beams with 40 segments, 5 beams with 25 segments and 4 beams with 20 segments. The dosimetric parameters were compared for the planned target volume (PTV). The dose of normal organs at risk (OARs) was also assessed. The monitor units and treatment times of the different IMRT plans were calculated. Results: The 20-segment IMRT plan significantly reduced the PTV maximum dose compared to the 40-segment IMRT plan. The 20-segment IMRT plan improved left kidney and liver dose sparing in V20 and V30 as well as the 40-segment IMRT plan did and provided better protection for the V20 (13.86±7.78) of the right kidney, the V30 (9.25±4.04) of the left kidney, the D mean (19.68±2.47) of liver and D max (38.79±3.57) of the spinal cord. Irradiation times in the         20-segment and 25-segment plans decreased by 2.5 and 1.9 min, respectively, compared to the 40-segment IMRT plan. Conclusion: IMRT using fewer beams and segments reduced delivery time without compromising plan quality in gastric cancer adjuvant radiotherapy. Fewer segments IMRT plans lowered the monitor units and the treatment time.