This dataset supports the manuscript “Diurnal Rhythm of the Human Plasma Proteome,” which investigates how protein concentrations in human plasma fluctuate over a 24-hour period. Using high-throughput mass spectrometry, we analyzed 208 high-quality plasma samples collected every three hours from 24 healthy individuals under tightly controlled conditions. Out of 523 quantified proteins, 138 (~26%) showed significant diurnal rhythmicity. These proteins were enriched in specific tissues, particularly the liver and platelets, and were involved in key biological pathways including hemostasis, immune signaling, and metabolism. Importantly, 36 clinically relevant biomarkers displayed time-of-day-dependent variation, highlighting the need to incorporate temporal factors in diagnostic and research protocols. This dataset offers valuable insights into circadian regulation of the plasma proteome and provides a resource for researchers studying time-sensitive biomarkers and physiological processes.