Photodynamic inactivation is one of the promising methods of combating a wide range of suspectible, but also resistant bacteria that are about to become a major problem in field of public health. The aim of this study was to investigate the effectiveness of photodynamic inactivation on resistant bacteria in municipal wastewater using cationic hydrophilic porphyrin TMPyP3 in combination with purple LED lamp with the intensity of 40 mW/cm2. The photodynamic effect was investigated by determining the miminum effective concentration (MEC) of TMPyP3 and photoinactivation testing. The study was carried out on multiresistant strains Pseudomonas aeruginosa and Burkholderia cepacia isolated from biofilm inside of hospital facilities and P. aeruginosa, Pseudomonas putida and Vibrio parahaemolyticus isolated from municipal wastewater. The tests were done on samples of sterile tap water, sterile wastewater and raw wastewater. By comparing the results, it was concluded that the effectiveness of TMPyP3 depends on the characteristics of tested strains and resistance mechanisms ( MEC for multidrug resistant P. aeruginosa in a sterile wastewater sample is ˃ 100 μM and MEC for suspectible P. aeruginosa under the same conditions is ˃ 12 μM). In addition, the results of photoinactivation test revealed that the efficacy of TMPyP3 in inhibition of multidrug resistant P. aeruginosa in raw wastewater sample was reduced due to the presence of other bacteria (% of inhibition of multiresistant P. aeruginosa in raw wastewater sample is ≈89% in comparison to ≈92% of inhibition in sterile wastewater) and that by prolongation of the irradiation time, the efficiency of the tested porphyrin increases at lower concentrations