This study evaluated growth performance and economic efficiency of a VietGAHP-based beef cattle fattening model in Phu Tho province over a 90-day period. The study compared two production systems: a VietGAHP model group (intensive) and a non-model group (traditional management). The household was used as the statistical unit; by randomly selecting k = 10 cattle per household, sample size with n = 5 households in the model group and n = 6 households in the non-model group. Average body weight increased from 248 to 347 kg/head in the model group and from 246 to 330 kg/head in the non-model group. Total dry matter intake (DMI) in the model group increased slightly across periods (9.22, 9.48, and 9.74 kg/head/day), whereas higher values were observed in the non-model group (9.61, 10.09, and 10.66 kg/head/day). The overall feed conversion ratio (FCR) for days 0–90 was 8.58 kg DMI/kg weight gain in the model group, lower than that in the non-model group (10.79 kg DMI/kg weight gain). An economic analysis standardized to 10 cattle per household, using a sale price of 75,000 VND/kg, showed that the model group achieved a profit of 23,814,000 VND/household/90 days, higher than the non-model group (6,894,000 VND/household/90 days). Corresponding economic efficiency was 10.07% and 2.87%, respectively. These results indicate that implementing VietGAHP can improve growth performance, feed utilization efficiency, and economic returns under smallholder conditions.