Objective: The objective was to evaluate effects of milk formula with Probiotics and Preoiotics (Synbiotic) on nutritional status and immune functions of children from 18 to 36 months old. Methods: In a randomized controlled trial. children were randomized to recein: a milk formula with or without Synbiotic for five months (400ml/day x 5 days/week). Length/height, weight and stool samples were collected at the beginning, middle and end of the intervention to evaluate weight and length gain and concentration of fecal slgA. Blood samples were collected at baseline and end of the trial to evaluate the concentration of hemoglobin. zinc, retinol and 1gA. Results: After 5 months of intervcntion. Synbiotic group showed a higher rate in weight and length gain (1.02 kg and 4.93 cm) comparcd to control group (0.63 kg and 3.89cm) with p 0.01. Concentration of hemoglobin, zinc and retinol were significantly improved in both groups compared to baseline. but there was no difference between Synbiotic and control group. Blood 1gA levels were significantly enhanced in the synbiotic group (62.82 mg/dL) compared to control group (57.42 mg/dL) with p 0.05. The concentration of fecal 1gA of control group was higher than control group at 2.5 and 5 months of intcrvention, however the difference is not statistically significant (p 0.05). Conclusion: Children who drink milk formula supplemented with Synbiotic showeda better improvement in weight and length gain and serum 1gA conccntration compared to those fed with control formula.