Background <p>Lactic whey, a significant agro-industrial byproduct, poses environmental risks due to its chemical composition. Despite various valorization efforts, effective utilization remains a challenge. This study explores the potential of <i>Neochloris oleoabundans</i>, a microalgae known for its metabolic versatility and resilience to adverse conditions, to produce exopolysaccharides (EPS) using lactic whey as a substrate. We compared EPS production from lactose, the primary sugar in whey, with whole lactic whey. Characterization of the EPS was performed using Fourier transform infrared spectroscopy (FT-IR) and gas chromatography–mass spectrometry (GC–MS), while morphological analysis was conducted via scanning electron microscopy (SEM). This research aims to assess the feasibility of converting lactic whey into valuable EPS, providing a sustainable approach to managing this agro-industrial waste.</p> Results <p>Lactic whey has produced the highest EPS and the FT-IR spectra revealed structural variations in the monomers which compose these polymers. Galactose and glucose were shown to be the primary monomers, according to GC–MS EPS analysis. SEM revealed a homogenous matrix and <i>N. oleoabundans</i>'s bioflocculant characteristics.</p> Conclusions <p>Microalgae <i>N. oleoabundans</i> can produce EPS using lactic whey as feedstock and it has the potential to be employed as a wastewater treatment.</p> Graphical Abstract <p></p>