Metformin and evogliptin are antidiabetic medications. Metformin works by lowering glucose production in the liver, delaying the absorption of sugar (glucose) from the intestines and increasing the body’s sensitivity to insulin. Evogliptin works by increasing the release of insulin from the pancreas and decreasing the hormones that raise blood sugar levels. This reduces fasting and post-meal sugar levels. An accurate and precise high-performance thin-layer chromatographic (HPTLC) method has been developed for the estimation of metformin and evogliptin. Aluminum HPTLC plates measuring 10 × 10 cm and 20 × 10 cm precoated with silica gel F254 was used for the chromatographic separation as the stationary phase, and a mixture of chloroform–methanol–ethyl acetate–formic acid (2:5.5:2:0.5, V/V) was used as the mobile phase. The method was linear in the concentration range of 1000–6000 ng/band and 10–60 ng/band of metformin and evogliptin, respectively, with a correlation coefficient of 0.99. The % recoveries at 50%, 100%, and 150% of both drugs, metformin and evogliptin, were found to be in limit of 98–102%. The method was found to be precise as the relative standard deviation (RSD) value was found to be 1.96 for metformin and 1.98 for evogliptin. The limit of detection was found to be 160.41 ng/band for metformin and 1.24 ng/band for evogliptin, while the limit of quantification was found to be 486.11 ng/band and 3.77 ng/band for metformin and evogliptin, respectively. The proposed method was validated with respect to linearity, accuracy, precision, and robustness as per the International Council for Harmonisation of Technical Requirements of Pharmaceuticals for Human Use ICH Q2 (R2) guideline. The kinetic degradation of the drugs was also studied and found to follow first-order kinetics as the value of K is constant at different intervals of time with the same temperature condition. The proposed validated HPTLC method can be used for the routine analysis of bulk drug, formulations, and stability samples.