The current study aimed to investigate the specific pathways in the offence process for mentally disordered firesetters. In a previous study, an offence chain model was constructed (i.e., the Firesetting Offence Chain for Mentally Disordered Offenders, FOC-MD) using offence descriptions obtained from 23 mentally disordered firesetters, detailing the sequence of contextual, behavioural, affective, and cognitive factors that precipitate an incidence of firesetting for this population. The current study examines the prevalence of the specific pathways to firesetting for the original 23 mentally disordered firesetters and a further sample of 13 mentally disordered firesetters. Three distinct pathways to firesetting are identified within the FOC-MD: fire interest–childhood mental health, no fire interest–adult mental health, fire interest–adult mental health. In this article, we describe these three pathways in detail using illustrative case studies. The practice implications of these identified pathways are also discussed.