<p>The growing concern over climate change and sustainability is promoting the development of partially bio-based unsaturated polyester resins (UPRs). However, being developed from renewable sources does not necessarily guarantee a better environmental profile for these materials, which justifies a detailed investigation of their environmental impacts. This paper presents a cradle-to-gate life cycle assessment (LCA) of five recently developed bio-based UPR formulations comprising renewably sourced chemical compounds, namely fumaric acid, dimer fatty acid, 2,5-furandicarboxylic acid, 1,3-propanediol, and isosorbide, as well as partially replacing styrene (50%) with 2-hydroxyethyl methacrylate as reactive diluent, considering inventory data from literature and purpose-made processes. As a benchmark, a typical oil-based UPR composition was also considered. The bio-based UPRs show improved environmental performance in various categories (e.g., climate change total, ozone depletion), reducing environmental impacts up to 90%. On the other hand, worse environmental performance was found in acidification, eutrophication (freshwater, terrestrial), and renewable primary energy impact categories. The main contributors to the higher impacts of the bio-based UPRs were found to be 2,5-furandicarboxylic acid, 1,3-propanediol, and 2-hydroxyethyl methacrylate. Fumaric acid and 1,3-propanediol have significant contributions to CO₂ sequestration. The single scores for the bio-based UPRs also show a reduction in impact ranging between 18 and 39% compared to the oil-based UPR.</p>