In this work, we studied the effect of TiO₂ sensitization with dry biomass extracted of cyanobacteria on the degradation of methylene blue dye (AM). Cyanobacterial cultures isolated from water samples were collected from the swamp of Malambo in Colombia; two main genera of cyanobacteria were identified, and they were cultivated with BG-11 culture medium. The concentrations of chlorophyll a in the exponential and stationary phases of growth were measured; the phycobilin content was quantified by spectrophotometry. Thin films of TiO₂ were deposited by a doctor blade method, and they were sensitized by wet impregnation. Furthermore, a methylene blue (MB) photodegradation process was studied under visible light irradiation on the cyanobacterial biomass sensitized TiO₂ material (TiO₂/sensitizer); besides, the pseudo-first-order model was used to obtain kinetic information about photocatalytic degradation. The results showed that the BG-11⁺ treatment reported a higher amount of dry biomass and phycobiliproteins. After the sensitization process, the TiO₂/sensitizer thin films showed a significant red shift in the optical activity; besides the thin film roughness decreasing, the TiO₂/sensitizer showed photocatalytic activity of 23.2% under visible irradiation, and besides, the kinetic (kap) constant for TiO₂/sensitizer thin films was 3.1 times greater than the kap value of TiO₂ thin films. Finally, results indicated that cyanobacterial biomass is a suitable source of natural sensitizers to be used in semiconductor sensitization.