In this study, the potential use of bacterial nano-cellulose (BNC) as powder (P), gel (G), and coated onto the fibers (C) on the mechanical and micro-structural properties of bagasse fiber–cement composites (FCCs) was explored. Results indicated that FCCs containing 6 wt.% fiber content manufactured with BNC-coated fibers and BNC gel enhanced mechanical properties and maximum hydration temperature (MHT). However, P FCCs exhibited inferior properties compared to C and G FCCs. According to Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM–EDX) analysis, the surface of BNC-coated fibers was rich in hydration products whilst penetration of alkaline ions into the lumen was reduced. BNC created both a strong interface with cement and prevented fiber mineralization.