Forensic nursing is a global and relatively young profession that combines nursing care and juridical processes. There are, however, significant differences in the qualifications of forensic nurses internationally. The aim of the study was to describe the professional competence profile of practising forensic nurses in Finland and to explore the effects of a 1-year further education programme on that competence profile. The data were collected in 2011–2012 using the Nurse Competence Scale comprising seven competence categories, and analysed using the software package SPSS version 19.0 (SPSS, Inc., Armonk, NY, USA). The participants were 19 forensic nurses and their 15 head nurses. The assessed overall scores from both informant groups indicated a high level of competence across the seven categories. The nurses felt that the overall competence level had increased during the education programme. The increase seen by the head nurses was smaller. The less frequent competence items included utilization of research and involvement of family in care. It can be stated that the 1-year further education programme was effective in developing the nurses' competence profile and, in particular, affected their professional self-confidence. It will, however, be essential to strengthen their skills for working with families and their awareness of evidence-based forensic nursing.