Gelatin zymography is a widely popular method due to its simplicity, low cost, and quick results, for studying gelatinases in various biological systems. Zymography can detect both the pro and active forms of matrix metalloproteinases MMP-2 (gelatinase A) and MMP-9 (gelatinase B). These MMPs play critical roles in the pathophysiology of many human diseases, particularly in cancer progression. Gelatin zymography is a method based on a suitable protein substrate incorporated into a sodium dodecyl sulfate–polyacrylamide gel. Substrate degradation by protease-containing samples can be visualized through the contrast between the Coomassie blue-stained gel and the white band of substrate degradation. Here, we provide a straightforward, step-by-step methodology for detecting MMP-2 and MMP-9 gelatinases in tumor cells. It is essential to highlight that accurately interpreting the data requires a thorough understanding of the technique’s principles.