Kiaran carried out his PhD in the Department of Biochemistry at the University of Sydney (1985-1988). From 1989 he was based at the Oxford University Laboratory of Physiology where he held an Oxford Nuffield Medical Fellowship and a Lister Institute Research Fellowship, as well as Research Fellowships at Wolfson and Exeter Colleges. He returned to Australia in 1996 to head the Department of Biochemistry and Molecular Biology in the ANU Faculty of Science, holding this post until June 2009 when he took up the position of Director of the newly-created ANU Research School of Biology. From 2014 to 2017 Kiaran served as the Dean of the ANU College of Medicine, Biology and Environment. Since August 2017 he has been Dean of the ANU College of Science.

Kiaran's major research interests are in the biology of the malaria parasite, with a particular focus on the mechanism of action of, and mechanisms of resistance to, antimalarial drugs.

Kiaran was elected a Fellow of the Australian Academy of Health and Medical Sciences (FAHMS) in 2017 and appointed Member of the Order of Australia (AM) in the 2023 Australia Day Honours.