Self-harm within the prison system is an under researched area, especially in the context of New Zealand. Previous research focusing internationally has found that there are multiple risk factors for self-harm while incarcerated, these risk factors include social interactions in prison, mental health, and prior histories of self-harming behaviours. This study expanded the knowledge of self-harm behaviours in the New Zealand context. Offenders who were incarcerated between 2016 and 2020 and had at least one incident of self-harm were included in the sample. Factors such as age, gender, custody status, and duration of incarceration were included in a latent class analysis to identify any underlying groups that were present in the data. The latent class analysis identified three classes of individuals based on self-harm behaviours: two low-risk classes and one high-risk class. The high-risk class had an over-representation of individuals with offences against property, females, and individuals on remand. The key differences between the three classes was the number of incidents per prisoner and the average duration of incarceration for each group. Overall, findings showed that a minority of individuals had the greatest risk of self-harm (the high-risk class). In addition, the majority of incidents occurred in the earliest months of incarceration, suggesting that this is a high-risk period for prisoners and that there is some form of adjustment period occurring when an offender enters the prison system; this was supported by the majority of offenders having one or fewer prior imprisonments, suggesting that prison was a new environment for most prisoners in the sample. Future research is required for greater understanding of the relationship between these two factors, particularly in the New Zealand context. What this study found largely aligns with previous research that a minority of individuals account for the majority of self-harm incidents, and that there is an overrepresentation of females in the self-harming data.