To evaluate the effect of photobiomodulation therapy on healthy joint's range of motion (ROM). Sixteen police working dogs were selected. The limbs of one side of the body were randomly assigned to the treatment group, while the limbs of the other side formed the control group. Elbow, stifle, and tarsal flexion and extension were evaluated, and measurements were made in triplicate by two evaluators, one experienced and one novice. After the initial evaluation, the treated side's joints underwent PBMT. The dogs had a 5-minute rest before the joint ROM was again measured. Digital thermography was also used to assess the joints before and immediately after PBMT, and after the 5-minute rest period. The variability of the joint median measurements was compared using 1-tail t-tests, and the effect size was determined. Following PBMT, significant differences in ROM were observed in all joints (p < 0.01) with a large effect size (0.84 to 0.96). Additionally, digital thermography values showed significant differences in all joints after PBMT (p < 0.01), with an increase of up to 5ºC, with a small to medium effect size (0.31-0.61). A significant difference was found for the stifle and tarsus after the 5 min (p < 0.01). There were no differences in the measurements by the two investigators. PBMT increased ROM and tissue temperature. This suggests that joint mobilization exercises can be improved by and should be conducted after PBMT. There was no significant difference between the measurements of experienced and novice evaluators.