Objective-To determine changes in Canine Brief Pain Inventory scores for dogs with osteoarthritis after administration of a monoclonal antibody (mAb) against nerve growth factor (NGF) that was modified by use of a proprietary process for administration to dogs. Animals- 11 adult dogs. Procedures- Dogs received the anti-NGF mAb (0.2 mg/kg, IV) at various evaluation times during the study period; at other evaluation times, dogs received an equivalent volume of PBS solution IV. Owners determined Canine Brief Pain Inventory pain severity (PS) and pain interference (PI) scores immediately before (baseline) and 2, 4, and 6 weeks after administration of the anti-NGF mAb; owners were unaware of the evaluation time at which the mAb had been administered. Results- Compared with baseline PS scores (median, 4.75; range, 0.75 to 8.5), dogs had significantly lower PS scores 2 weeks (median, 3; range, 1 to 5.5) and 4 weeks (median, 2.25; range, 0.25 to 7.25) after administration of anti-NGF mAb. Compared with baseline PI scores (median, 5.33; range, 1.17 to 9.33), dogs had significantly lower PI scores 2 weeks (median, 3; range, 0.67 to 6.83) and 4 weeks (median, 3.33; range, 0.67 to 6.67) after administration of anti-NGF mAb. The PS and PI scores 6 weeks after mAb administration were lower than baseline scores, although values were not significantly different. Conclusions and Clinical Relevance- Results of this study suggested the evaluated anti-NGF mAb decreased PS and PI scores for 4 weeks after administration. This treatment may be effective for alleviation of signs of pain in dogs with osteoarthritis for up to 4 weeks.