Blood outgrowth endothelial cells (BOECs) have received growing attention in relation to cardiovascular disease (CVD). However, the effect of diet intervention, a primary strategy for CVD prevention, on BOECs is not reported. This study aims to investigate the effect of following a healthy dietary pattern (HDP) with or without wolfberry consumption, healthy food with potential cardiovascular benefits, on the number and function of BOECs in middle-aged and older adults. Twenty-four subjects consumed either an HDP only (n = 9) or an HDP supplemented with 15 g day-1 wolfberries (n = 15) for 16 weeks. At pre- and post-intervention, vascular health biomarkers and composite CVD risk indicators were assessed. BOECs were derived from peripheral blood mononuclear cells and their angiogenic and migration activities were measured. Isolated BOECs have typical endothelial cobblestone morphology, express von Willebrand factor and KDR. Consuming an HDP improved the BOEC colony's growth rate, which was demonstrated by significant time effects in the colony's culture time between passages 1 and 2 (P = 0.038). Both interventions increased BOECs' tube formation capacity. Moreover, HDP intervention contributed to a time effect on BOEC migration activity (P = 0.040 for t1/2gap). Correlation analysis revealed that BOEC colony number was positively associated with blood pressure, atherogenic index, vascular age, and Framingham risk score. In conclusion, adherence to an HDP improved BOECs' function in middle-aged and older populations, while additional wolfberry consumption did not provide an enhanced effect. Our results provide mechanistic dissection on the beneficial effects on BOECs of dietary pattern modification.