The purpose of this study was to assess the effects of hydration status on cardiac function and hematological factors at rest and during psychological stress. Volunteers participated in an initial visit (Session 1), a pre fluid-load visit (Session 2), and a post fluid-load/stress manipulation visit (Session 3). At each session, blood pressure (SBP, DBP), heart rate (HR), and total body water (TBW) were obtained. At Session 2, participants were assigned to either an Enhanced Hydration (EnH) or Non-Enhanced (NE) condition. The EnH Group drank 6 liters of water over 3 days proceeding Session 3. During Session 3, cardiac and hematological measures were recorded during a seated baseline, math task, and a cold pressor task. Session 1 analyses revealed significant inverse relationships for males between DBP and TBW. At session 3, participants in the EnH Group displayed greater HR at rest compared to the NE Group. Stress-reactivity analyses for the math task revealed significant Group differences on DBP with the NE Group displaying greater DBP reactivity compared to the EnH Group. These results indicate differential effects of hydration status on cardiac function while at rest and during psychological stress.