This study used microwave-assisted hydrothermal (MHT) methodology to successfully synthesize highly crystalline perovskite-type NaTaO3. Calcination at 800, 850 and 900°C was performed to evaluate MHT’s effects on NaTaO3’s crystallinity, optical properties, morphology and photocatalytic performance. Grain growth-induced irregular agglomerations reduced the surface area of the calcined samples, negatively affecting photocatalytic performance. TaO bond of sodium tantalum was detected in all samples by FTIR spectra analysis, proving the success of MHT. Based on the results of photocatalytic experiment using methyl-blue aqueous solution under both UV and visible (white-light LED) light irradiation, the non-calcined NaTaO3 performed better than the calcined ones. Thus, calcination does not always guarantee a better photocatalytic performance of NaTaO3. The performance of the non-calcined NaTaO3 exposed to five hours of visible light irradiation (60%) was less positive than that exposed to UV irradiation (90%). This photocatalyst holds promise for the treatment of wastewater in the future.