The paper associated with this dataset describes the effects of microfibres, a common type of microplastics, in direct membrane filtration of wastewater. The dataset contains: a) experimental data from membrane performance testing and calculations (transmembrane pressure, fouling resistance, fouling constants, cake foulant mass, specific cake resistance), and b) material characterisation data for microfibres, membranes and foulants (Fourier Transform Infrared Spectroscopy (FT-IR) spectra, Scanning electron microscope (SEM) images, Total Organic Carbon (TOC) concentrations, fluorescence Excitation-Emission Matrices).