Herein, we report a new class of biosourced nanofiltration membranes based on chemically recyclable aliphatic polyesters (P(4,5-T6GBL)) and the use of green solvents. Given their chemical recyclability and potential biodegradability, these polyester membranes were designed to have a sustainable lifecycle. The effect of membrane thickness and solvent/non-solvent diffusivity on membrane morphology and organic solvent nanofiltration were investigated. Long-term membrane stability was tested in a continuous crow-flow filtration rig over a week, which exhibited stable methanol permeance at 8.6 ± 0.1 L m−2 h−1 bar−1. The rejection profiles of the pharmaceuticals oleuropein (540 g mol−1) and roxithromycin (837 g mol−1) were also found to be stable at 87% and 100%, respectively.