Type A acute aortic dissection is a life-threatening vascular emergency because of its high morbidity and mortality. Platelet is a pivotal ingredient involved in the development of acute aortic dissection. In this study, we aimed to investigate whether mean platelet volume (MPV)/platelet count ratio predicts in-hospital complications and long-term mortality in type A acute aortic dissection. In this single-center and prospective cohort study, 106 consecutive patients with Stanford type A acute aortic dissection admitted to the hospital within 12 h after onset were recruited. The best cut-off value of MPV/platelet count ratio predicting all-cause mortality was determined by the receiver operator characteristic analysis. Patients were divided into high (H-MPV/platelet count) and low (L-MPV/platelet count) groups based on the cut-off value of 7.49 (102 fl/109/l). Patients were followed up for 3.5 years. Of the 106 acute aortic dissection patients, 71 (67.0%) died during the study period, with a median follow-up duration of 570 days. Compared to the L-MPV/platelet count group, patients with H-MPV/platelet count had a higher risk of in-hospital complications including hypotension, hypoxemia, myocardial ischemia/infarction, conscious disturbance, pericardial tamponade, paraplegia, and poor survival (all P < 0.05). In multivariable Cox regression models adjusted for potential confounders, MPV/platelet count ratio was positively associated with the hazard of all-cause mortality, irrespective of interventions either with medication only or urgent surgery, and the hazard ratios were 2.81 (95% confidence interval 1.28–4.48) for the H-MPV/platelet count group when taking L-MPV/platelet count group as the reference (P = 0.005). The MPV/platelet count ratio was a strong independent predictor for in-hospital complications and long-term mortality in patients with type A acute aortic dissection.