White spot lesions are one of the concerns during the fixed orthodontic treatment. Thus, the aim of the present study was to evaluate the antimicrobial/anti-inflammatory effect of curcumin-photodynamic antimicrobial chemotherapy (c-PACT) and chlorhexidine varnish on the plaque accumulation and gingival bleeding in adolescents under fixed orthodontic treatment. A randomized clinical trial was performed with an initial number of 45 patients being distributed into three groups: group I-chlorhexidine varnish 2%, group II-placebo varnish, and group III-c-PACT (curcumin at 1.5 mg.mL(-1)) exposed to blue Light-emitting diode (LED) light at 450 nm (power density = 165 mW.cm(-2), fluency = 96 J.cm(-2), total dose = 150.7 J). The treatments were performed for four consecutive times with an interval of 1 week each. After the interventions, two calibrated examiners (Kappa value = 0.75) analyzed the dental plaque accumulation by plaque index (PI) and gingivitis condition by gingival bleeding index (GBI) with 1 and 3 months of follow-up after the treatments comprised a final sample of 35 patients. No significant difference was found to PI between the groups during baseline and 1-month period. Group III (1.52 ± 0.51) presented significance difference from group I (0.91 ± 0.75) and group II (1.03 ± 0.51) at 3 months of follow-up. In this same period, there was more plaque accumulation with significant statistical difference (P ≤ 0.05) in comparison to the other periods to all studied groups. There was a GBI reduction statistically significant to groups I and III at 1-month follow-up in comparison to other periods. No effect was verified to dental plaque accumulation after the photodynamic application mediated with curcumin activated with a blue LED light.