This study investigated the corrosion inhibition performance of Sida acuta leaf extract on aluminium in an acidic medium, focusing on its phytochemical constituents, inhibition efficiency, and statistical modelling. A quadratic model developed using Response Surface Methodology (RSM) assessed the influence of immersion time, temperature, and extract concentration. Experimentally, inhibition efficiency increased with concentration, reaching values above 80% at higher extract dosages under moderate temperature conditions (20 - 40 °C). However, efficiency declined to below 60% at an elevated temperature of 60 °C, while extended immersion for 168 h resulted in a 20 - 25% reduction, demonstrating susceptibility to thermal degradation and inhibitor desorption. The model produced a coefficient of determination (R²) of 0.8039, accounting for about 80% of the variation in inhibition efficiency. The Adjusted R² (0.7317) and Predicted R² (0.5951) showed reasonable agreement, while the Adequate Precision value of 14.17 exceeded the minimum acceptable threshold of 4, indicating a strong signal-to-noise ratio. Model reliability was further supported by a coefficient of variation (CV) of 7.44%, a standard deviation of 5.04, and a PRESS value of 764.86, confirming acceptable predictive accuracy. Diagnostic evaluations affirmed model adequacy, showing normal residual distribution, absence of influential outliers (Cook’s distance 80%) and eco-friendly inhibition under optimized conditions, supported by robust statistical indicators (R² = 0.8039; Adequate Precision = 14.1692; CV = 7.44%), validating its potential as a sustainable corrosion inhibitor.