Background Prior research has classified firesetters by motive. The multi‐trajectory theory of adult firesetting (M‐TTAF) takes a more aetiological perspective, differentiating between five hypothesised trajectories towards firesetting: antisocial cognition, grievance, fire interest, emotionally expressive/need for recognition and multifaceted trajectories. Aim The objective of this study was to validate the five routes to firesetting as proposed in the M‐TTAF. Methods All 389 adult firesetters referred for forensic mental health assessment to one central clinic in the Netherlands between 1950 and 2012 were rated on variables linked to the M‐TTAF. Cluster analysis was then applied. Results A reliable cluster solution emerged revealing five subtypes of firesetters – labelled instrumental, reward, multi‐problem, disturbed relationship and disordered. Significant differences were observed regarding both offender and offence characteristics. Discussion Our five‐cluster solution with five subtypes of firesetters partially validates the proposed M‐TTAF trajectories and suggests that for offenders with and without mental disorder, this classification may be useful. If further validated with larger and more diverse samples, the M‐TTAF could provide guidance on staging evidence‐based treatment. Copyright © 2015 John Wiley & Sons, Ltd.