Adults with intellectual disability are disproportionately represented in criminal justice systems, yet evidence on their offending patterns remains fragmented. This systematic review aimed to synthesize empirical findings on offence types, trajectories, associated risk factors, and criminal justice responses among adults with intellectual disability. A systematic review was conducted in accordance with PRISMA 2020 guidelines. Searches of PubMed, Scopus, Web of Science, PsycINFO, and Criminal Justice Abstracts identified 670 records. After duplicate removal, 192 unique records were screened by title and abstract, followed by full-text assessment of 54 articles. A total of fifteen studies that passed the inclusion criteria were included in the qualitative synthesis. Studies that passed the eligibility criteria included all adult (≥ 18 years) and diagnosed with intellectual disability studies that had quantitative or qualitative offending patterns or justice observations reported. Study selection, data extraction, and quality appraisal were performed independently by two reviewers. The heterogeneity in the study design and outcome measures led to a narrative synthesis. Studies that included had found increased cases of adults with intellectual disability in violent and sexual offending that were mostly correlated with psychiatric comorbidity, autism spectrum disorder, adverse childhood experiences, and social disadvantage. Incidents were usually unplanned and more spontaneous than planned. Institutional and forensic pathways prevailed, and even moderate offences were noted to be held in long periods of detention. There was little evidence on recidivism and the gender-specific route. Modularized cognitive behavioural interventions were shown to be slightly effective, especially in the case of sexual offending. Adult intellectual disability offending is cumulative in vulnerability and systemic as opposed to criminal intent. The community-based interventions and disability-informed practices in justice are required to lessen the criminalization and enhance the results.