Background: Various lines of research point to the overrepresentation of individuals with intellectual disability (ID) in the criminal justice system. Studies have also shown that individuals with ID are vulnerable to mental health problems. To date there have been no Canadian studies of individuals with an ID in the criminal justice system. Method: The present study reports on the sociodemographic, mental health and criminological characteristics of 281 individuals with an ID from a Canadian study of men in a pre-trial holding centre. Results: Almost 19% of the men had a probable ID, and nearly one-third (29.9%) were in the borderline IQ range. As was the case for their non-ID counterparts, the mean age of the probable ID group was in the early 30s, few were employed, and most had low incomes. Individuals in the probable and borderline ID groups had lower rates of high school completion than those in the average intellectual ability range. Over 60% of individuals with an ID had a substance use disorder, and 1 in 5 was intoxicated at the time of assessment. These rates were similar across groups, and to those found in the literature. A large majority of individuals with ID had a previous conviction, and most had previously committed a violent offence. Conclusions: Among other limitations, the sample may not have been entirely representative of the total population of men in the pre-trial detention centre, given the relatively high refusal rate (39.5%). Results are discussed in terms of orienting criminological and mental health services as a function of the level of intellectual and adaptive functioning of individuals with ID. (Contains 2 tables, 1 figure and 1 note.)