© 2018, Australian Ceramic Society. The objective of this study is to produce potassium lanthanum titanate (K 2 La 2 Ti 3 O 10 , KLTO)-based coatings with Nd, Gd, and Sm dopants by using sol-gel method to degrade the color of methylene blue azo dye from water and to evaluate the acute toxicity of water. Phase identification and morphology of K 2 La 1.1 Nd 0.9 Ti 3 O 10 , K 2 La 1.9 Gd 0.1 Ti 3 O 10 and K 2 La 1.5 Sm 0.5 Ti 3 O 10 coatings were characterized through X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Photocatalytic degradation tests of methylene blue azo dyes were performed with KLTO-based coatings using Atlas Suntest CPS+ solar simulator. Photocatalytic absorbance measurements were investigated with Schimadzu UV-Vis 1240 spectrometer. Acute toxicity tests were evaluated to determine toxicity of methylene blue dyed water using Daphnia magna. In addition, to find acute toxicity of methylene blue treated with photocatalyst, the tests were carried out daylight and dark ambient at 20 ± 2 °C. It was found that samples with KLTO-based coatings demonstrated higher photocatalytic activity than blank sample. As a result of high photocatalytic activity, methylene blue samples treated with photocatalysts showed less toxic performance than blank sample according to acute toxicity tests. According to photocatalytic performance experiments and acute toxicity tests, doped K 2 La 1.5 Sm 0.5 Ti 3 O 10 photocatalysts showed less-toxic effect and higher photocatalytic degradation performance.