Bacterial cellulose nanofibers (BCNFs) produced from freeze-dried bacterial cellulose (BC) exhibit unique properties such as low cost, flexibility, environmental friendliness, and structural stability. In this study, a novel catalyst, BCNF-CPTMS-Gu-Cu(II), was successfully fabricated by modifying BCNFs with 3-(chloropropyl)-trimethoxysilane (CPTMS) and guanidine hydrochloride (Gu) to create ligand-functionalized BCNFs, followed by the stabilization of copper(II) nanoparticles on guanidine groups. This synthesis process maintained the original morphology of BCNFs. The BCNF-CPTMS-Gu-Cu(II) catalyst demonstrated excellent catalytic activity for the rapid reduction of 4-nitrophenol (4-NP) and methylene blue (MB) in the presence of sodium borohydride (NaBH₄). For the reduction of 4-NP to 4-aminophenol (4-AP), the catalytic activity of BCNF-CPTMS-Gu-Cu(II) was optimized by increasing NaBH₄ concentration and reaction temperature. It was observed that higher temperatures positively affected the reaction rate. Similarly, for the reduction of MB to leuco-methylene blue (LMB), the catalytic efficiency was enhanced by increasing the NaBH₄ concentration and optimizing the pH, with the best catalytic performance achieved at pH 6. The reduced products, 4-AP and LMB, are highly soluble in water and have potential utility in various applications. This study introduces an effective and low-cost catalyst based on bacterial cellulose nanofibers, with promising applications in industrial processes.