Wet chemical synthesis of nanomaterial has earned reputation for producing size and shape controlled nanomaterials with fair reproducibility. In the present work, size controlled tin oxide nanoparticles have been synthesized by chemical precipitation method using SDS as capping agent. X-ray diffraction spectra (XRD) confirm the formation of tetragonal rutile SnO2 nanoparticles with average crystallite size in the range of 25-35 nm. Fourier Transform Infrared Spectroscopy (FTIR) complimented the XRD results with the peak of Sn-O-Sn stretching at 643 cm(-1). Surface morphology of prepared nanoparticles has been studied with the help of scanning electron microscopy (SEM). A direct band gap of 2.97 eV has been calculated for the synthesized nanoparticles using UV-Vis spectra and Tauc plots. Synthesized nanoparticles show excellent photocatalytic degradation of water pollutant dye congo red and also illustrate antimicrobial action against human pathogen bacteria Pseudomonas aureginosa and Staphylococcus aureus.