Background: Computed tomography (CT) is essential for diagnosis, but its use of ionising radiation requires clear patient communication and informed consent. This study assessed knowledge, perception and communication needs regarding CT imaging among adult patients at Benjamin Mkapa Hospital, Tanzania. Methods: A hospital-based cross-sectional mixed-methods study was conducted among inpatients and outpatients attending CT services. Quantitative data were collected from 224 patients using a structured interviewer-administered questionnaire, and qualitative data were obtained through 18 semi-structured interviews. Descriptive statistics, association tests, regression analysis and thematic analysis were used. Findings were integrated through triangulation. Results: Overall, 43.8% of participants had low CT knowledge, 37.9% had moderate knowledge and 18.3% had high knowledge. Although 65.6% knew that CT produces cross-sectional images, only 40.6% identified CT as ionising radiation and 30.4% knew that CT usually delivers more radiation than a plain chest X-ray. Trust in healthcare providers was high, while pre-scan anxiety was moderate. Adequate knowledge was associated with receiving an explanation before CT, higher education and previous CT experience. High anxiety was more common among female and first-time CT patients, but was lower among those who received explanations. Conclusion: Patients accepted CT mainly through professional trust, but radiation knowledge and interactive communication were limited. Standard pre-CT explanations, simple information materials and targeted support for first-time patients may strengthen informed consent and reduce avoidable anxiety. The findings highlight a practical patient-education gap within routine Tanzanian tertiary imaging services.