Methylene blue (MB) is a widely used cationic dye whose persistence, strong coloration, and potential toxicity pose significant environmental threats when discharged into aquatic ecosystems. Natural biosorbents have gained attention as cost-effective materials for dye remediation. Among them, modified Abies marocana biomass has demonstrated promising adsorption performance, achieving an initial MB removal efficiency of 96.5% under optimized conditions. To ensure its practical applicability in wastewater treatment, evaluating the regeneration and reusability of the biosorbent is essential. This study focuses on assessing the regeneration behavior of sulfuric-acid-treated A. marocana needles (AMNS) following MB saturation. Chemical regeneration was carried out using an acid-elution approach, in which the effects of eluent concentration and contact duration were examined. The regenerated biosorbent underwent several adsorption–desorption cycles, and its performance was monitored using UV–Vis spectrophotometric measurements to determine the recovery of adsorption efficiency after each cycle. The AMNS biosorbent exhibited strong regeneration capacity, maintaining a substantial proportion of its initial performance after repeated reuse. Over three successive cycles, the regenerated material retained 80–90% of its original adsorption capacity, indicating efficient desorption of MB molecules and limited degradation of surface functional groups. These results suggest that the chemical modification applied to A. marocana enhances its structural stability and resilience during regeneration. The findings highlight the potential of modified Abies marocana biomass as a durable and reusable adsorbent for the treatment of MB-contaminated wastewater. Its high initial removal efficiency, combined with strong regeneration performance, supports its integration into sustainable, low-cost water treatment systems. The regeneration behavior confirms that AMNS can be effectively reused over several cycles without significant loss of adsorption capacity, reinforcing its value as an environmentally friendly biosorbent.