Professor Ussher joined St George's in 1999 as a Research Fellow and PhD student. On completion of his PhD (2001), Professor Ussher was appointed as a Lecturer. He was promoted to Senior Lecturer in 2006, Reader in Health Psychology in 2010 and received his Chair in Behavioural Medicine in 2013. In 2013, Professor Ussher was also awarded the Hamid Ghodse Foundation Chair in Addiction, in recognition of his research on smoking cessation. From 2015-2018 Professor Ussher was appointed as Associate Dean for Widening Participation. Since 2018 he has divided his time between St George's and the University of Stirling, where he is also Professor of Behavioural Medicine. Professor Ussher acts as a consultant for the Department of Health (DoH) on tobacco control.