In 1986, he became the first junior doctor appointed to the newly established psychiatric department at Akureyri Regional Hospital. Just over a year later, he moved with his family to Norway, where he worked at institutions including Ullevål Hospital in Oslo, Blakstad Hospital in Asker and the National Centre for Epilepsy in Sandvika. He received his specialist certification in psychiatry in 1992.

After qualifying as a specialist, Ásgeir spent many years working in geriatric psychiatry units in Norway, first at Blakstad Hospital and later at Søndre Borgen in Asker, where he served as Chief Physician for nearly a decade. He later contributed to the development of an outpatient clinic in Oslo before joining Diakonhjemmet Hospital in Oslo, where for the past 20 years he has worked in consultation-liaison psychiatry.

Ásgeir has also been actively involved in the Norwegian Psychiatric Association for decades, particularly within the fields of geriatric psychiatry and consultation-liaison psychiatry. His main areas of expertise are geriatric psychiatry and consultation-liaison psychiatry.