<p>Drought stress is main abiotic constraint restrictive maize (<i>Zea mays</i> L.) growth worldwide. An effective agricultural approach to enhance its growth under this stress is the plant growth-promoting microorganism’s application. In this study, <i>Trichoderma harzianum</i> isolate Zag-1 was evaluated for its potential to mitigate drought-induced damage in maize plants. At first, <i>T. harzianum</i> was isolated from pepper plant’s rhizosphere soils, and its growth-promoting characteristics were assessed, including indole-3-acetic acid (IAA), hydrolytic enzymes (chitinase, amylase, and cellulase), ammonia production, and zinc and phosphorus solubilization, all of which showed positive results, confirming its growth-promoting attributes. Besides, an in vivo experiment was conducted under controlled greenhouse conditions by withholding irrigation until soil moisture dropped to ~ 45% field water capacity (FWC) for 15 days. Four treatments are used: (1) well-watered control (90% field water capacity, FWC), (2) <i>T. harzianum</i>-inoculated under well-watered conditions, (3) drought-stressed (45% FWC), and (4) <i>T. harzianum-</i>inoculated+ drought-stressed. After 15 days of drought application, morphological (shoot height, in addition shoot and root fresh and dry weights), physiological (Chl a and b, relative water content [RWC], and membrane stability index [MSI]) and biochemical (osmolytes [proline, proteins and total soluble sugars] and antioxidant enzyme activities) assessments were recorded. The results indicated that shoot (39.44 and 37.92%) and root (10.29 and 28.77%) fwt and dwt, leaf RWC (7.90%), total pigment content (24.49%) and MSI (9.40%) decreased in drought-stressed maize while an increase in their membrane lipid peroxidation (77.21%), electrolyte leakage (EL) (48.04%) and hydrogen peroxide (128.94%) contents were noted versus the control plants; however, <i>T. harzianum</i>-treated plants showed the reverse responses. <i>T. harzianum</i>-treated maize plants revealed significant boosts in growth and physiology under stress paralleled to untreated ones, along with a notable enhancement in antioxidant defense activity (21.20 and 8.53% for POD and APX). Moreover, under stress, osmoprotectants, including proline (23.78%) and soluble sugars (12.28%) were markedly greater in <i>Trichoderma</i>- inoculated plants than non-inoculated. Our results recommend that <i>T. harzianum</i> is an effective, sustainable biotechnological tool for drought resilience in maize. Therefore, exploring and optimizing the application of <i>T. harzianum</i> addresses the broader goals of resource recycling, environmental sustainability, and climate-smart agriculture.</p>