Background: Tooth decay and traumatic dental injuries are the main causes of pulp inflammation in primary teeth. The present study was conducted on photodynamic therapy for endodontic treatment of primary teeth. Materials & Methods: 40 primary anterior teeth with pulp necrosis were divided into 2 groups: Group I, conventional root canal therapy and group II, conventional root canal therapy combined with antimicrobial PDT. Each group with 20 patients. Microbiological samples of the intra-canal content were taken using paper cones. Results: Group I & II had 19 boys and 9 girls and 8 boys and 12 girls respectively. Colony-forming units (CFU/mL) before and after treatment in group I at sample 1, 2, 3, 4, 5, 6, 7, 8, 9& 10 were 94000 and 0, 87040 and 2433, 14530 and 0,154231 and 4500, 123145 and 3200, 28453 and 550, 110232 and 1250,112456 and 3100, 43294 and 0 and 142945 and 1955 respectively. CFU before and after treatment in group II at sample 1,2,3,4,5,6,7,8,9 &10 were 194000 and 248,187040 and 2450,24530 and 0, 254231 and 4200,23140 and 300,38453 and 430,120232 and 1280, 212438 and 3600,143294 and 0 and 242940 and 1924 respectively. Conclusion: Conventional treatment combined with antimicrobial PDT found to be equally