Objective: To compare the inter-rater reliability and usability of two delirium screening tools designed for use in ICU; the Confusion Assessment Method for ICU and the Intensive Care Delirium Screening Checklist. Research methodology/design: A multiple methods design was used. The intra and inter rater reliability of the tools were evaluated using Kappa statistics and intra class correlation coefficients. Focus groups were conducted to explore ICU staff perceptions of the usability of the tools and feasibility of delirium screening. Setting: Private hospital ICU, Melbourne Australia. Results: 66 patients were assessed for delirium; median age of 71 (IQR 62–75) years. Seventeen patients (26%) scored positive for delirium using the screening tools and 11 (17%) had delirium confirmed on the medical ICU discharge summary. Ten nurse assessors performed 99 paired assessments using the two tools sequentially, demonstrating the intra and inter-rater agreement and reliability of the tools was moderate to high. Four focus groups were conducted with 16 participants. Content analysis identified three themes: (i) current recognition of delirium, (ii) benefits of delirium screening, and (iii) future directions for delirium management. Time and medical staff indifference were identified as barriers to screening, facilitators were education and having a follow-up plan. Conclusion: This study found that the reliability and usability of the CAM-ICU and ICDSC were acceptable and that using structured delirium screening was feasible as part of a wider, multi-disciplinary delirium management plan.