Obtaining plasma from a blood sample and preparing it for subsequent analysis is currently a laborious process involving experienced health-care professionals and centrifugation. We circumvent this by utilizing capillary forces and microfluidic engineering to develop an autonomous plasma sampling device that filters and stores an exact amount of plasma as a dried plasma spot (DPS) from a whole blood sample in less than 6 min. We tested 24 prototype devices with whole blood from 10 volunteers, various input volumes (40-80 μL), and different hematocrit levels (39-45%). The resulting mean plasma volume, assessed gravimetrically, was 11.6 μL with a relative standard deviation similar to manual pipetting (3.0% vs 1.4%). LC-MS/MS analysis of caffeine concentrations in the generated DPS (12 duplicates) showed a strong correlation ( R2 = 0.99) to, but no equivalence with, concentrations prepared from corresponding plasma obtained by centrifugation. The presented autonomous DPS device may enable patient-centric plasma sampling through minimally invasive finger-pricking and allow generatation of volume-defined DPS for quantitative blood analysis.