Aim and background: Glass ionomer cement (GIC) possess properties to fulfill the prerequisites of a restorative material for atraumatic restorative treatment (ART). Enhancing the antibacterial property of GIC remains the pressing priority to reduce the occurrence of secondary caries. Thus, this study aimed to evaluate and compare the setting time and antibacterial efficacy of cinnamic acid (CA)-incorporated GIC against Streptococcus mutans and Lactobacillus acidophilus. Materials and methods: CA powder was incorporated into the GIC powder in varying concentrations. For testing the setting time, the total samples of 15 disks were divided into five groups, namely—I: control—unmodified GIC, II: 2.5% CA + GIC, III: 5% CA + GIC, IV: 7.5% CA + GIC, and V: 10% CA + GIC. Setting time was evaluated after 30 seconds of mixing the powder and liquid by lowering a flat-end needle indentor. Similarly, for testing the antibacterial efficacy against S. mutans and L. acidophilus, the samples were divided, and 5 disks were allocated to each subgroup. The disks were placed in agar diffusion plates, which were inoculated with cultured test species separately. After 24 hours of incubation, the zone of inhibition (ZOI) was measured. Results: CA-modified GIC exhibited an increase in setting time and ZOI with the increase in concentration of CA, and this difference was found to be statistically significant between the groups. Conclusion: CA-incorporated GIC has greater antibacterial efficacy against the caries-causing bacteria with an acceptable change in setting time. Clinical significance: GIC with higher antibacterial potential can markedly decrease the occurrence of secondary caries and failure of restorations.