This study was carried out to investigate the antioxidant properties of synbiotic product, Lactobacillus acidophilus supplemented with 2.5% royal jelly in skim milk and Bifidobacterium bifidum supplemented with 7.5% royal jelly in skim milk, using DPPH (1,1-Diphenyl-2-picrylhydrazyl) radical scavenging assay, reducing power, total antioxidant in linoleic acid system and formation of diene-conjugation assay. Results showed that the synbiotic effect of royal jelly and probiotic bacteria provided substantial antioxidant activities. Fermented milk samples by B. bifidum supplemented with 7.5% royal jelly and L. acidophilus supplemented with 2.5% royal jelly exhibited high scavenging activity with 96.8 and 93.3%, respectively at a concentration of 500 µg/mL. IC50 values were estimated with 226.7 µg/mL for B. bifidum supplemented with 7.5% royal jelly and 210.2 µg/ml for L. acidophilus supplemented with 2.5% royal jelly. On the other hand, L. acidophilus supplemented with 2.5% royal jelly and B. bifidum supplemented with 7.5% royal jelly exhibited significantly high reducing power at a concentration of 1000 µg/mL. The percentages of peroxide inhibition of L. acidophilus supplemented with 2.5% royal jelly and B. bifidum and 7.5% royal jelly were 52% and 42%, respectively. Significant inhibitions were found in the formation of conjugated diene with 66.9% and 65.8% for L. acidophilus with 2.5% royal jelly and B. bifidum with 7.5% royal jelly, respectively. These results were compared with standards BHT, ascorbic acid and trolox.