Dr John Hennessy's Albury-based Oral and Maxillofacial practice commenced in 1978 and has evolved into a comprehensive specialist medical and dental facility servicing Albury-Wodonga, Griffith and Wangaratta regions and patients as far removed as the South Coast of New South Wales and Southern Victoria.

In keeping with his commitment to regional Australia, Dr Hennessy co-founded a multi-disciplinary Facial Deformity Clinic in 1981 facilitating, in conjunction with the region's orthodontic specialists, the management of patients requiring correction of congenital or trauma-related facial deformities.

Dr Hennessy is also an inaugural member of the Head and Neck Clinic (for the treatment of cancer) at the Murray Valley Private Hospital; a clinic staffed by Oral and Maxillofacial, Radiation Oncology, Medical Oncology and Ear, Nose and Throat Specialists.

Dr Hennessy is called upon to lecture locally, regionally and nationally to medical and dental students and professionals and to nursing and community organisations.