<p>Chromium (Cr), especially in its hexavalent form, is a potent carcinogen and poses significant environmental risks due to its persistence in soil and water. To this end, the current study investigated Cr toxicity and its amelioration by proline in cluster bean. The plants were raised in sand spiked with 2 and 4&#xa0;µg g^− 1 Cr (Cr2 and Cr4) and proline was applied as seed priming (PP) and exogenous (EP) application to sand. The growth attributes and rate of photosynthesis in cluster bean decreased by Cr whereas proline content and electrolyte leakage were increased. The application of proline mitigated the toxic effects of Cr. However, proline acted more efficiently as exogenously than seed priming. The EP applied to Cr2-stressed plants enhanced the plant height and biomass production. EP treatment enhanced shoot fresh weight (95.3%), root fresh weight (85.7%) and shoot dry weight (144.8%) in Cr2-stressed plants and root dry weight (153.85%), net photosynthetic rate (93.97%) and transpiration rate (114.1%) in Cr4 stressed plants. Compared to Cr-stressed plants, catalase (CAT), glutathione reductase (GR) and guaicol peroxidase (GPX) activities were reduced in EP treatment. The integrity of the plasma membrane was retained after EP in Cr-stressed plants. The results suggest that the adverse effects of Cr toxicity in cluster bean can be mitigated more effectively by EP compared to PP.</p>