[2] Pearn went on to attain a bachelor's degree in science (BSc) at the University of Queensland, subsequently graduating with First Class Honours in Medicine and Surgery (MBBS) in 1964.

[3] Pearn went on to complete a PhD on spinal muscular atrophy at the University of London, with his work defining the classical clinical classification of disease severity.

In addition to formal postings, Pearn has served in various non-Corps positions, including training officer of the New Guinea Volunteer Rifles and defense platoon commander of London's 4th Battalion, The Royal Green Jackets.

[9][10][11] Professor Pearn has completed major research studies in accident prevention; and optimal methods of pre-hospital care (particularly of poisoned, envenomed or near-drowned victims).

[13] Pearn continued his dedication to the Scouting movement into adulthood, serving as a Councilor and as Vice President of the Queensland Branch.

[15] [7] Pearn served for over 40 years with St John Ambulance Australia, a charitable body dedicated to helping people in sickness, distress, suffering or danger.

[7][12][16][17] For three decades, Pearn was the national Medical Adviser for the Child Accident Prevention Foundation of Australia (now Kidsafe)[2], of which he was a co-founder.

[21][22] The plant species Androcalva pearnii was named in Pearn's honour, in recognition of his contributions to medicine, education, humanitarianism and as an author of medical and botanical works.

[17] In 2016, Pearn was personally presented the King Edward VII Cup for outstanding international service to lifesaving by Her Majesty, Queen Elizabeth II.

[16] Pearn was awarded Member of the Order of Australia (AM) in the Australian 1979 Queen's Birthday Honours List for services to medicine, particularly in the field of child health.

The Queensland Branch of the Australian Dental Association conferred the Award of Merit upon Pearn in 2000 in recognition of his many supportive roles to the field of dentistry.

[28] In 2002, Pearn was awarded the prestigious Howard Williams Medal by the Division of Pediatrics and Child Health of the Royal Australasian College of Physicians.

The International Life Saving Federation awarded Pearn their Medal for Meritorious Service in honour of his seminal work in the area of childhood drowning and prevention.

The Human Genetics Society of Australasia invited Pearn to deliver its annual peak event, the HGSA Oration, in 2011.

In 1995, Pearn was invited to deliver the Sherrington Oration at The University of Oxford on the topic "Humanitarianism at War" after three decades of service as a doctor-soldier in the Royal Australian Army Medical Corps.