| Zeolites, with their dual capacity for water retention and nutrient provision, offer a promising solution to enhance crop resilience under moisture-deficient conditions. To evaluate the effects of zeolite on biochemical traits, chlorophyll fluorescence, and coriander seed yield under water-limited conditions, a two-year (2018–2020) factorial experiment was conducted at the Zendeh Rooh research station in Jopar, Kerman Province, Iran. The study followed a randomized complete block design (RCBD) with three replications. The first factor comprised three irrigation levels: 100% (non-stress), 75% (moderate stress), and 50% (severe stress) of the crop’s water requirement, applied via drip (tape) irrigation. The second factor included five zeolite application rates: 0, 2, 4, 6, and 8 tonnes per hectare (t/ha). The results indicated that all traits studied were significantly affected by the main effects of moisture regimes and zeolite, as well as their interaction effects. Water deficit significantly reduced photosynthetic efficiency (Fv/Fm, ΦPSII), chlorophyll content (Chl C), photochemical quenching (qP), relative water content (RWC), and seed yield (SY), while increasing non-photochemical quenching (NPQ), proline content (PC), and relative membrane permeability (RMP). Zeolite application mitigated these adverse effects by enhancing Chl C, RWC, Fv/Fm, qP, and ΦPSII, while suppressing NPQ, PC, and RMP. Maximum yields occurred at 100% irrigation with 8 t/ha (1,109 kg/ha) and 6 t/ha (1,095 kg/ha). Under 75% and 50% irrigation, 8 t/ha zeolite yielded 893 kg/ha and 608 kg/ha respectively—outperforming 6 t/ha by 6.6% and 4.9%. For optimal coriander productivity in semi-arid regions such as Kerman, Iran, we recommend 6 t/ha zeolite under non-stress or moderate water stress (75–100% irrigation). Under severe drought (50% irrigation), 8 t/ha zeolite is advised to maximize seed yield. These findings highlight zeolite’s potential as a sustainable strategy for water-scarce agroecosystems in Iran and climatically similar regions globally. |