Switchable-hydrophilicity solvent liquid-liquid microextraction was coupled with smartphone digital image colorimetry for the determination of palladium as its metal chelate with N,N-diethyl-N'-benzoylthiourea. Images of the colored extract were captured in a homemade colorimetric box, which were split into their red-green-blue channels. The blue channel was used to determine the concentration of palladium. Optimum extraction conditions were achieved using 600 mu L of triethylamine as the extraction solvent and 4.0 mL of 10 M sodium hydroxide as the hydrophilicity-switching trigger within 1.0 min extraction time. Optimum complexation conditions were obtained at a sample pH of 4.50, and metal/ligand mole ratio of 1:2 within 3.0 min. Optimum detection conditions were achieved at a distance of 7.0 cm between the sample solution and the detection camera, a region of interest of 175.0 px(2) at a detection wavelength of 480.0 nm and 30.0% brightness of the monochromatic light source. Limits of detection and quantitation were found to be less than 0.7 and 1.8 mu g g(-1), respectively. A good linearity with coefficients of determination above 0.9974 was obtained. Accuracy was checked via a single-factor analysis of variance (ANOVA) test by comparing the results with the ones obtained using flame-atomic absorption spectrometry and the results were statistically in a good agreement (P > 0.05). The proposed method was applied for the determination of palladium in catalytic converters with percentage relative recoveries ranging between 95.7 and 103.7% and percentage relative standard deviations below 4.0%.