Endothelial cells (ECs) are located at the interface between flowing blood and the vessel wall, and abnormal EC proliferation induced by pathologic environments plays an important role in vascular remodeling in hypertensive conditions. Exchanges of information between blood components and ECs are important for EC function. Hence, the present study sought to determine how platelets induce EC dysfunction under hypertensive conditions. EC proliferation was increased in renal hypertensive rats established by abdominal aortic coarctation compared with control rats and that elevated thrombin in plasma promoted platelet activation, which may induce the release of platelet‐derived microparticles (PMPs). MicroRNA (MiR) array and qPCR revealed a higher level of miR‐142–3p in platelets and PMPs. In vitro, PMPs delivered miR‐142–3p into ECs and enhanced their proliferation via Bcl‐2‐associated transcription factor (BCLAF)1 and its downstream genes. These results indicate that PMPs deliver miR‐142–3p from activated platelets into ECs and that miR‐142–3p may play important roles in EC dysfunction in hypertensive conditions and may be a novel therapeutic target for maintaining EC homeostasis in hypertension.—Bao, H., Chen, Y.‐X., Huang, K., Zhuang, F., Bao, M., Han, Y., Chen, X.‐H., Shi, Q., Yao, Q.‐P., Qi, Y.‐X. Platelet‐derived microparticles promote endothelial cell proliferation in hypertension via miR‐142‐3p. FASEB J. 32, 3912–3923 (2018). www.fasebj.org