In this study, we innovatively explored the utilization of almond peel to synthesize lignin-NPs through a singular and cost-effective hydrothermal process. The research delved into a comprehensive analysis of the structural and optical characteristics of the synthesized lignin-NPs through a suite of techniques including FT-IR, XRD, TEM, EDX/FESEM, UV–Vis, and Photoluminescence (PL). UV–Vis spectra showed the maximum wavelength at 280 nm, confirming the NPs’ synthesis. According to PL spectroscopy, lignin-NPs emitted fluorescent light at 551 nm. Also, FTIR and XRD patterns confirmed nanoparticle synthesis with crystallinestructure. The TEM and FESEM images showed spherical morphology with an average size of 9.97 nm. The stability of nanoparticles was assessed utilizing zeta potential analysis (−23 mV) and DLS showing a PDI around 0.2. The cytotoxic effect of lignin-NPs was investigated on Huh-7 and normal L929 cell lines using the MTT assay and the result showed that no significant toxicity was observed on normal L929 cells after 48 h, but IC50 value for cancer Huh-7 cells was about 597.2 µg/mL. A photocatalytic test revealed that lignin-NPs degrade Methylene Blue (90 %, MB), Eriochrome Black T (89 %, EBT), and Rhodamine B (85 %, RhB) pigments under UVA light after 60 min.