Recycling of textile waste materials has attracted significant attention for fabrication low-cost dye adsorbent from aqueous solutions. Viscose cellulosic waste fibers are supposed to give an answer to the finding low-cost adsorbent materials. In this research work, viscose waste fibers (VF) were modified by selective oxidation to improve the ability to absorb cationic dyes during wastewater treatment. For this purpose, different treatment parameters were investigated such as sodium periodate concentration, and time of selective oxidation with sodium chlorite. Then, unmodified and oxidized viscose fibers (OVF) were ball milled to produce viscose powder (VP) and oxidized viscose powder (OVP), respectively. The morphology of obtained viscose powders was characterized by scanning electron microscopy. Furthermore, methylene blue adsorption onto viscose cellulose fiber waste (VF) and oxidized viscose fibers (OVF) was studied as a function of contact time (0–80 min), adsorbent dosage (1–9 g/L), MB solution initial pH (3–9) and MB initial concentration (20–80 mg/L). The results showed that MB adsorption onto VF and OVF is a rapid favorable chemisorption process that can be well described by the Langmuir model. The higher adsorption capacity of OVF than VF was related to the increase of the carboxylic group. The oxidized viscose fiber can be used as a potential adsorbent for water treatment.