Background and Objective Photodynamic therapy (PDT) and antiresorptive drugs, such as alendronate (ALN), have been shown to reduce alveolar bone loss. The aim of this study was to evaluate the possible synergic effects of combining PDT and ALN on bone loss in periodontitis in rats. Material and Methods Periodontitis was induced by ligature in 60 Wistar rats randomized into the following groups: control (Group 1); PDT (Group 2); ALN 0.01 mg/kg (Group 3); ALN 0.25 mg/kg (Group 4); PDT + ALN 0.01 mg/kg (Group 5); and PDT + ALN 0.25 mg/kg (Group 6). The rats were killed on day 12 and the mandibles were processed for macroscopic morphometric analysis, micro‐computed tomography to analyze bone mineral density (BMD) and histological analysis. Gingival samples were collected to evaluate myeloperoxidase (MPO) and malonaldehyde (MDA) levels. Results Bone loss and inflammatory activity in histological studies, from the greatest to least was: control > ALN 0.01 mg/kg > PDT > ALN 0.25 mg/kg > PDT + ALN 0.01 mg/kg > PDT + ALN 0.25 mg/kg, while the order from least to greatest BMD was: control < ALN 0.01 mg/kg < PDT < ALN 0.25 mg/kg < PDT + ALN 0.01 mg/kg < PDT + ALN 0.25 mg/kg. The order of MPO and MDA activity from greatest to least was: control > ALN 0.01 mg/kg > PDT > ALN 0.25 mg/kg > PDT + ALN 0.01 mg/kg > PDT + ALN 0.25 mg/kg. The positive results obtained in the group treated with PDT + ALN 0.25 mg/kg showed statistically significant differences (P ≤ .05) compared with the other 5 groups for BMD, MPO and MDA. Conclusion Combined approach therapy of PDT + ALN 0.25 mg/kg demonstrated a protective effect on alveolar bone loss.