Þórir has extensive experience in plastic surgery and is a practicing specialist at the Department of Plastic Surgery at Landspítali and the Department of Breast Surgery at Landspítali. He is also an assistant professor of plastic surgery at the University of Iceland.

After completing his residency at the Academic Hospital in Sweden in 2004, he continued to work there as a specialist. He did further postgraduate training in microsurgery at the prestigious Chang Gung Medical Hospital in Taiwan in 2006-2007. He was then chief physician in the plastic surgery department at the Academic Hospital until 2013. During those years, he also worked part-time at the Art Clinic in cosmetic surgery and at the First Hospital in Stockholm in abdominal and pelvic floor reconstruction after major abdominoplasty. In 2013, he founded Nordic Plastic Surgery and worked as a consultant and lecturer, especially in breast reconstruction, at the University Hospital in Stavanger, Trondheim and at the Akershus Hospital in Oslo. From 2015 to 2018, he was chief physician at Riskhospitalet in Oslo. He has been working full-time at the National Hospital since 2019.

He has extensive experience in breast surgery, augmentation, reduction, fat grafting, pad removal and performs all types of breast reconstruction. He has extensive experience in facial surgery and is responsible for adult facial plastic surgery at Landspítali. He has treated patients with Botox for about two decades. He has published numerous peer-reviewed articles and teaches plastic surgery at Landspítali.