In this study, surface, bulk, and hemocompatibility characteristics of crosslinked, bi-soft segment poly (ester urethane urea) membranes, prepared by extending a poly(propylene oxide)-based triisocyanate-terminated prepolymer (PU) with a polycaprolactone diol (PCL), were investigated. Variation of the ratio of PU to PCL diol content in the membrane formulation yielded alteration of surface energy, phase morphology both in the bulk and in the region near the surface, and it affected hemocompatibility. Nearly all membranes were nonhemolytic, with hemolysis degrees between 1 and 2.1% and, for short-time contact with blood (15 min), all membranes showed in vitro thrombosis degrees between 27 and 42%. The membranes prepared with 5 and 25% of PCL diol showed almost no adherent platelets. These two membranes had a higher hard segment aggregation in the region near the surface and mixing between the two soft segments in the bulk, but showed contrasting surface energy characteristics. The results obtained in this work give evidence that surface energy and its polar and dispersive components did not correlate with any of the hemocompatibility aspects studied. In contrast, the phase morphology in the region near the surface was a major influence on membrane hemocompatibility.