Background: Remnant cholesterol in triglyceride-rich lipoproteins is associated observationally and genetic, causally with increased risk of atherosclerotic cardiovascular disease in healthy individuals. Objectives: We tested the hypothesis that an unmet medical need exists in individuals with high nonfasting remnant cholesterol and prior atherosclerotic cardiovascular disease. Methods: From amongst 109 574 individuals in a prospective cohort study of the Danish general population, we included 2973 individuals aged 20–80 with baseline diagnoses of myocardial infarction/ischaemic stroke ascertained from national Danish health registries. Results: The recurrent major cardiovascular event (MACE) incidence rates per 1000 person-years were 39 (95% confidence interval: 30–50) for individuals with remnant cholesterol levels ≥ 1.5 mmol L⁻¹ (≥58 mg dL⁻¹), 31 (26–37) for 1–1.49 mmol L⁻¹ (39–57 mg dL⁻¹), 27 (24–31) for 0.5–0.99 mmol L⁻¹ (19-38 mg dL⁻¹) and 23 (19–27) for individuals with remnant cholesterol < 0.5 mmol L⁻¹ (<19 mg dL⁻¹). Compared to individuals with remnant cholesterol < 0.5 mmol L⁻¹ (<19 mg dL⁻¹), the subhazard ratio for recurrent MACE was 1.23 (95% CI: 0.98–1.55) for individuals with remnant cholesterol levels of 0.5–0.99 mmol L⁻¹ (19–38 mg dL⁻¹), 1.48 (1.14–1.92) for 1–1.49 mmol L⁻¹ (39–57 mg dL⁻¹) and 1.79 (1.28–2.49) for ≥ 1.5 mmol L⁻¹ (≥58 mg dL⁻¹). The recurrent MACE incidence rates per 1000 person-years for individuals with remnant cholesterol levels < 0.5 mmol L⁻¹ (<19 mg dL⁻¹) and ≥ 1.5 mmol L⁻¹ (≥58 mg dL⁻¹) were 10 (6.6–15) and 31 (21–47) for those below age 65 and correspondingly 25 (21–30) and 43 (32–59) for those with LDL cholesterol levels < 3 mmol L⁻¹ (<116 mg dL⁻¹), respectively. For a 20% recurrent MACE risk reduction in secondary prevention, an estimated remnant cholesterol lowering of 0.83 mmol L⁻¹ (32 mg dL⁻¹) would be needed. Conclusions: In individuals with a diagnosis of myocardial infarction/ischaemic stroke, a lower remnant cholesterol of 0.8 mmol L⁻¹ (32 mg dL⁻¹) was estimated to reduce recurrent MACE by 20% in secondary prevention. Our data indicate an unmet medical need for secondary prevention in individuals with high nonfasting remnant cholesterol levels.