Calcium-based photocatalysts represent an economic and available alternative for the photodegradation of distinct pollutants such as pesticides, pigments, colorants, and drugs, among others. In the following paper, the morphological, structural, optical, and textural properties of a series of materials based on calcium carbonate (calcite) modified with Tin and their evaluation in phenol photodegradation were studied. The synthesized materials were characterized by several techniques, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), N2 adsorption–desorption at 196 °C, Diffuse Reflectance Spectroscopy (DRS), Scanning Electron Microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS). The characterization information indicated that a portion of Sn4+ was incorporated into calcite structure and the rest crystallized as SnO2. The effect of tin incorporation was also evidenced by the calculated bandgap values whereas the tin amount increased the values got close to SnO2 value. Neither the bare sample SnO2 nor CaCO3 presented photoactivity for phenol mineralization. Nevertheless, it was demonstrated that the modified calcites presented a photocatalytic activity comparable to P25-TiO2, carrying out phenol mineralization in 3 h. Tin-modified calcite compounds were obtained by a controlled coprecipitation method. The photocatalytic evaluations presented a photocatalytic activity comparable to P25-TiO2, which was assigned to tin presence in a low-value material such as calcite.