Dr. Dennis McCullough grew up in a suburb of Philadelphia and was inspired at a young age, both through Delaware County 4-H Club and a number of veterinarians, to pursue a career in Veterinary Medicine. He graduated from the University of Scranton in 1973, with a Bachelor of Science in Pre-Med Biology, and from the University of Pennsylvania in 1977, with a Veterinary Medical Doctorate (VMD).

After practicing Veterinary Medicine for two years in Camp Hill, Pennsylvania, he opened the Waynesboro Veterinary Clinic in October of 1979. He and his wife, Dianne, a licensed Veterinary Technician, ran the practice on their own for two years, before it became necessary to hire employees. In January 2018, Dr. McCullough sold the practice to his daughter-in-law, Dr. Mikie Dawson and his youngest son, Patrick. Patrick has replaced Dianne, as the Practice Manager. 2019 marks the 40th Anniversary of the Waynesboro Veterinary Clinic offering veterinary medical and surgical services, to the greater Waynesboro area.

Dr. McCullough is a strong believer in education and has consistently attended over 50 hours of continuing education each year to stay as informed as possible on the latest advances and techniques in Veterinary Medicine. He has always had a number of hobbies outside of work, including woodworking, automotive refurbishing, tennis, scuba diving, archery, and wine-making just to name a few. He also enjoys spending time with his wife, his 3 children and their spouses, and his 8 grandchildren.