Methylene blue (MB) dye is a common pollutant in industrial wastewater. This study evaluates the adsorption efficiency of NaOH-activated date pits biochar, neutralized with vinegar, for MB removal. Date pits biochar obtained at 450° was activated with a 1 M NaOH solution and neutralized to pH 7 using vinegar. Adsorption experiments were conducted at MB concentrations (5, 20, and 35 ppm), biochar dosages (1, 2, and 3 g/L), and stirring times (15–35 min). Results revealed significant adsorption efficiency, up to 97.6% at 5 ppm concentration, 2 g/L dosage, and 35 min stirring. However, adsorption efficiency decreased at higher MB concentrations, indicating the biochar’s capacity limitations. Statistical analysis using the Response Surface Methodology (Box-Behnken design) confirmed that the initial dye concentration and biochar dosage significantly influenced the removal efficiency of MB. FTIR analyses highlighted the biochar’s adsorption behaviour and the responsible functional groups. This study presents the vinegar-neutralized NaOH-activated biochar as an environmentally friendly solution for wastewater treatment and recommends further optimization of the process.