Background: Rapid identification of coronary heart disease may improve clinical outcomes in patients presenting with acute chest pain. We aimed to establish whether early CT coronary angiography in intermediate-risk patients presenting to the Emergency Department with acute chest pain could improve one-year clinical outcomes. Methods: In a prospective randomised open blinded-endpoint parallel-group clinical trial, adults with suspected acute coronary syndrome and prior coronary heart disease, elevated cardiac troponin or ischaemic electrocardiogram, were randomised 1:1 to early CT coronary angiography plus standard of care or standard of care alone in 37 UK hospitals. The primary endpoint was one-year all-cause death or subsequent type 1 or 4b myocardial infarction. Findings: Between 23rd March 2015 and 27th June 2019, 1748 participants (mean age 62 (SD 13) years, 64% male, mean GRACE score 115 (SD 35)) were randomised to early CT coronary angiography (n=877) or to standard of care alone (n=871). The primary endpoint occurred in 51 (5·8%) participants randomised to CT coronary angiography and 53 (6·1%) participants with standard of care (adjusted hazard ratio 0·91 (95% confidence interval, 0·62 to 1·35), P=0·65). CT coronary angiography was associated with reduced invasive coronary angiography (adjusted hazard ratio 0·81 (95% confidence interval, 0·72 to 0·92), P=0·001) but no change in coronary revascularisation or preventative therapies. Early CT coronary angiography was associated with longer hospitalisations (median increase 0·21 (95% confidence interval 0·05 to 0·40) days) and higher costs (£561 more per patient). Interpretation: In patients with suspected acute coronary syndrome, CT coronary angiography did not alter overall coronary therapeutic interventions or one-year clinical outcomes but increased length of hospital stay and healthcare costs. These findings do not support the routine use of early CT coronary angiography in intermediate-risk patients with acute chest pain. Trial Registration: ISRCTN19102565 and NCT02284191. Funding Statement: National Institute for Health Research HTA Programme (13/04/108). Declaration of Interests: SG was deputy director of the National Institute for Health Research Health Technology Assessment Programme and chairs the NIHR HTA commissioning committee. NC reports Unrestricted research grants from HeartFlow, Boston Scientific, Haemonetics, Beckmann Coulter Speaker fees and Consultancy from HeartFlow, Boston Scientific, Abbott, Haemonetics Travel sponsorship from Haemonetics, Boston Scientific, HeartFlow, Biosensors, Edwards, Medtronic. DEN reports grant support from Siemens. All other authors report no conflicts of interest. Ethics Approval Statement: The trial was approved by the South East Scotland Research Ethics Committee 01.