Lefteris is a counselling psychologist and lecturer in psychology and counselling at Monash University. In his counselling practice, teaching and research, Lefteris adopts the framework of intersectionality whereby individuals' multiple identities intersect to create novel experiences of mental health and illness while operating as both protective and risk factors. As a psychologist, Lefteris has worked extensively with clients with issues relating to migration, grief, trauma and LGBTQI+ identities. He has also worked with clients with a variety of mental health issues, court-ordered parents and their children, and individuals and couples pursuing artificial reproductive treatment. Lefteris has a particular research interest in the wellbeing, grief and belonging of LGBTQI+ young people and adults and migrant populations.
Lefteris is the course leader of the Master of Counselling. The Master of Counselling is one of the largest courses at Monash University and it is offered in Australia (on-campus and online), Singapore and Hong Kong.