With more than 10% of the world’s population lacking access to clean drinking water, the World Health Organization recognizes the ever-growing water crisis as a leading global risk to human health. Additionally, ∼1.7 billion people have access to improved drinking water that suffers from poor microbial quality, leading to the death of a child every 19 seconds. Polymer membranes are an enabling technology for society to meet the ever-increasing demand for clean water. While previous research has aimed to improve the longevity of membranes, advances made to one membrane property often adversely affects another. For example, increases in membrane flux often reduce membrane selectivity. Here, for the first time, we have synthesized and characterized ultrafiltration membranes with a high-porosity nanofiber top-layer using electrospun nanofibers. To decouple the effect of nanofiber chemistry from morphology, polymers commonly used in the membrane industry, cellulose and polysulfone (PSf), were electrospun into a 50 µm thick layer comprised of randomly accumulated 1 µm diameter fibers. When applied as a top layer, the nanofibers did not change membrane selectivity and high pure water flux persisted or, in the case of the PSf nanofibers enhanced membranes, permeability was 35% higher than the base membranes. Next, the effect of altering the properties of the electrospun nanofiber layer (i.e., fiber diameter and bulk layer thickness) were systematically investigated. Thicker PSf nanofiber layers (50 µm to 125 µm) and thinner individual fiber diameters (1.0 to 0.4 µm µm) exhibited further increases in pure water fluxes. Additionally, our nanofiber enhancement improved oil fluxes and decreased protein retention by >90% when compared to the base membranes. Furthermore, surface chemistry of the nanofibers was modified to improve protein fouling resistance in dynamic long-term testing. In the final portion of this work, I will demonstrate how controlling the deposition of polydopamine enabled the immobilization of poly(ethylene glycol) and a polymer zwitterion onto the surface of ultrafiltration membranes with retained membrane function and improved antifouling performance. This work demonstrates that high porosity electrospun nanofibers hold potential to serve as a versatile materials platform to improve the performance of ultrafiltration membranes for water treatment and pharmaceutical purification.