A major problem in world health care is the development of antibiotic resistance in bacteria. In light of this, pure and calcium-doped zinc tin oxide (ZTO) nanoparticles, Zn 2 SnO 4 (S 1 ), Zn 2 Sn 0.7 Ca 0.3 O 4 (S 2 ), Zn 2 Sn 0.5 Ca 0.5 O 4 (S 3 ), and Zn 2 Sn 0.3 Ca 0.7 O 4 (S 4 ), were synthesized via simple and cost effective microwave assisted method. The doping effect on antibacterial activity was studied in detail. The XRD spectrum revealed that all the deposited samples exhibited a spinel cubic structure. A decrease in crystallite size, an increase in strain and dislocation density was observed with an increase in Ca concentration. FESEM images exhibited an irregular and non-homogeneous nature with crystalline morphology having a physical dimension of nm size. EDAX confirmed the purity of deposited samples. We used the agar well diffusion technique to study the antibacterial activity of Gram-positive and Gram-negative bacteria. The doping of the ZTO matrix with Ca ions increased its antibacterial performance by 99% against Klebsiella pneumoniae bacteria, and its effectiveness was enhanced with increasing Ca ion concentration inside the Zn 2 SnO 4 nanoparticles.