Enhancing the availability of soluble silicon (Si) is essential for activating drought tolerance mechanisms in crops. Our investigative study aimed to evaluate the potential of silicon nanoparticles (nSi) to trigger defense responses against drought stress during the acclimation of sugarcane cultivars. A field experiment was conducted using a randomized block design in a split-split plot arrangement with two irrigation regimes (80% and 40% of field capacity), two nSi levels (with and without 2.0 mM nSi), and two sugarcane cultivars (RB867515 and RB027040). After 140 days of drought, physiological and morphological parameters were assessed, including growth, gas exchange, water status, photosynthetic pigments, and relative drought tolerance. nSi supplementation significantly alleviated drought-induced damage in the RB027040 cultivar, enhancing fresh and dry biomass and improving relative drought tolerance. These effects were linked to increased net photosynthesis in both cultivars and enhanced stomatal conductance in RB027040 under drought. The findings indicate that nSi promotes photosynthetic efficiency and biomass accumulation, supporting drought resilience. Overall, nSi emerges as a promising tool for the sustainable management of sugarcane in water-limited environments.