Once thought of as simple anucleate fragments with a sole role in hemostasis, platelets are now recognized as versatile cellular effectors with a range of functions beyond primary hemostasis. They carry a wealth of molecular information, including messenger RNAs (mRNAs), which reflect their complex roles. The advent of next-generation RNA sequencing (NGS) has revolutionized the study of platelet mRNAs, revealing that transcripts from about half of the human genome are present in these terminally differentiated cells. Platelet mRNAs share many characteristics with those in nucleated cells, and studies have shown that platelets can translate certain megakaryocyte-derived mRNAs into proteins. Furthermore, platelet mRNA profiles can be used to predict cellular functions, and platelets can transfer intact mRNAs to microparticles and other cells. This chapter provides an updated review of our current understanding of platelet mRNAs, their potential as biomarkers, and their contributions to both biological and pathological processes.