In Australia, the terms dual diagnosis and comorbidity are commonly used, often interchangeably, to describe the experience of consumers with both mental health difficulties and difficulties with alcohol and other drug use. Consumers with comorbidity often have complex needs that require comprehensive assessment, multidisciplinary team support, and trauma-focused management. More information about the demographics of consumers admitted with comorbidity, and the documented assessed needs, care, and interventions provided, would provide the foundations for working towards improved quality and continuity of care. Therefore, the aim of this study was to explore the documentation of inpatient assessment, care, and interventions provided to people with comorbidity. The research design was a retrospective exploratory study, and data collection involved a 12-month healthcare record audit. Forty-one records were screened, and 36 consumer healthcare records were identified as eligible for inclusion in the study. Most consumers (n = 34, 94%) were admitted on an involuntary basis, and 8 (22.2%) were female. Consumers had a median length of stay of almost six months. In most healthcare records, there was no documented evidence of care planning involvement by consumers or the multidisciplinary team. There was great variance in the delivery of nonpharmacological interventions. Most consumers did not receive trauma-focused assessment or intervention, and assessment tools were often incomplete with outcome measures poorly documented. This study has demonstrated significant gaps in consumer and multidisciplinary engagement with care planning and goal setting. There was poor documentation of comprehensive assessment and nonpharmacological interventions.