<p>Purpose Nickel (Ni) toxicity has emerged serious threat to agricultural productivity worldwide. Plant source activator could be used as a green economic chelate to remediate the Ni-polluted soils. However, the positive responses of calotropis leaf extract (CLE) for Ni phytoextraction using <i>Mathiola incana</i>, is unknown. Methods At first, Ni rates (0, 25, 50, 100, 200, 400, 600, 800, 1000&#xa0;mg kg^− 1 of soil) were optimized using <i>M. incana</i> as a test plant. The Ni (600&#xa0;mg kg^− 1) was optimized that caused minimum negative effects on plant growth (40%) and uptake surplus Ni contents (63%). In second study, plants were further grown under two Ni levels (0 and 600&#xa0;mg kg^− 1) and treated with CLE (0, 5, 10, 20, 30, 40%) to alleviate Ni adversities. Results CLE at 20% significantly enhanced the net photosynthesis (9.10 µmol CO₂ m^− 2 s^− 1), chlorophyll <i>a</i> (0.70 mg g^− 1 FW) and carotenoids (0.18 mg g^− 1 FW) under Ni toxicity. CLE-treated plants at 20% had higher values of catalase (40.01 U mg^− 1 protein), superoxide dismutase (135.15 U mg^− 1 protein) and membrane stability index (24%) to Ni stress. Exogenous CLE application at 20% markedly lowered the melondialdehyde (16%) and hydrogen peroxide (32%) contents for increased plant height (31.67&#xa0;cm) and shoot dry weight (4.87&#xa0;g) than no CLE supply. Moreover, 20% CLE application also enhanced the Ni in shoot (253.40&#xa0;mg kg^− 1), bio-concentration factor (2.09) and translocation factor (3.74) against Ni stress. Conclusions Hence, CLE (20%) was found to be an efficient candidate for chemical replacement to promote the phytoextraction capacity through increased physiological activities in <i>M. incana</i>.</p> Graphical Abstract <p></p>