Objectives This study sought to evaluate the prognostic value of coronary artery calcium score (CACS) and coronary computed tomography angiography (CTA) for major adverse cardiac events (MACE). Background The prognostic value of CACS has been well described. Few studies use the rich information of coronary CTA to predict future clinical outcomes and compare CACS with coronary CTA. Methods We followed up 5,007 outpatients who were suspected of having coronary artery disease (CAD) and who underwent cardiac CTA. Cardiac CT was assessed for CACS and the extent, the location, the stenosis severity, and the composition of the plaque in coronary CTA. The endpoint was MACE, defined as composite cardiac death, nonfatal myocardial infarction, or coronary revascularization. Results Follow-up was completed in 4,425 patients (88.4%), with a median follow-up period of 1,081 days. At the end of the follow-up period, 363 (8.2%) patients had experienced MACE. Cumulative probability of 3-year MACE increased across CT strata for CACS (CACS 0, 2.1%; CACS 1 to 100, 12.9%; CACS 101 to 400, 16.3%; and CACS >400, 33.8%; log-rank p < 0.001); for coronary CTA (no plaque 0.8%, nonobstructive disease 3.7%, 1-vessel disease 27.6%, 2-vessel disease 35.5%, and 3-vessel disease 57.7%; log-rank p < 0.001); and for characteristics of the plaques (5.5% for calcified plaque, 22.7% for noncalcified plaque, and 37.7% for mixed plaque; log-rank p < 0.001). The area under the receiver-operating characteristic curves showed the incremental value of CACS and coronary CTA for predicting MACE: 0.71 for clinical risk factors, which improved to 0.82 by adding CACS and further improved to 0.93 by adding coronary CTA (both p < 0.001). Conclusions The CACS and coronary CTA findings have prognostic value and have incremental value over routine risk factors for MACE, and coronary CTA is superior to CACS. Cardiac CT seems to be a promising noninvasive modality with significant prognostic value.