This study aims to investigate the in-vitro quality control and physicochemical properties of different marketed brands of diclofenac sodium tablet. The research will involve conducting various laboratory tests, including weight variation test, content uniformity test, drug assay, friability test, and the disintegration and dissolution test. Three brands of diclofenac sodium tablets were used in the study, named brand A, brand B & brand C. Quality control (QC) test results for diclofenac sodium tablets shows that brand A, brand B & brand C confirm to the Indian pharmacopeia (IP) standards. In terms of weight variation, brand A, B & C have an above the mean weight limit variation of 1.288%, 1.222% and 2.538 respectively. The lower mean weight limit variations are 1.377%, 1.052% and 1.522% respectively, which are within the 7.5% standard limits of IP. Friability tests show that brands A, B and C have an average friability of 0.090%, 0.029% and 0.050% mass loss, which are within the1% mass loss limits of IP. In terms of drug assay, All brands A, B and C fall under the IP parameter of 90%-110%,respectively.The disintegration test shows that brand A, brand B and brand C fall within a 20-minute time interval segment with disintegration time calculated as14min,14.2 min and 15.3 min for brands A,B and C respectively. Brand A, B and C of diclofenac sodium has a drug dissolution percentage of 97.77%, 98.26% and 99.23% respectively within a 45-min sampling time interval. Keywords: Diclofenac sodium, quality control testing, weight variation, disintegration, friability, dissolution, drug assay by Non aqueous titration and UV spectrophotometry.