The discharge of dye-containing industrial effluents such as methylene blue (MB) in water bodies has resulted in severe aquatic and human life problems. In addition to this factor, there is the accumulation of banana peel wastes, which can generate ecological damage. Thus, this research purpose a different method from the literature using the banana peel waste (BP) to produce activated carbon (ACBP) by NaOH activation followed by pyrolysis at 400 °C to remove methylene blue (MB). The material was characterized by TGA, XRD, SEM, BET, and FTIR. The influence of dye concentration (10, 25, 50, 100, 250, and 500 mg L−1) was investigated. ACBP presented a well-developed pore structure with a predominance of mesopores and macropores. This morphological structure directly influences the MB removal capacity. The highest efficiency for dye removal was in the MB initial concentration of 25 mg L−1, sorbent of 0.03 g, and contact time of 60 min, which were 99.8%. The adsorption isotherms were well defined by Langmuir, Freundlich, and Temkin isotherm models. The Langmuir model represented the best fit of experimental data for ACBP with a maximum adsorption capacity of 232.5 mg g−1. This adsorbent showed a comparatively high performance to some previous works. So, the banana peel waste is an efficient resource for producing activated carbon and the adsorption of methylene blue.