Mechanical strength, transparency and flexibility are the leading bottlenecks for the application of a membrane. Thus, the development of co-effectively strong, transparent and flexible membranes is significant for various industries. Here, we fabricated the ANFs (aramid nanofibers)/BC (bacterial cellulose) nanocomposite membranes with different ANFs loadings (up to 8.0 wt%) via a facile and simple vacuum-assisted flocculation route. FT-IR, XRD and SEM were applied to characterize the pure BC membrane and ANFs/BC nanocomposite membranes. The resultant membranes maintained excellent transparency and flexibility at relatively low ANFs concentrations (≤4.0 wt%). The mechanical properties of ANFs/BC nanocomposite membranes could be altered by changing the ANFs content, in which the ANFs served as an enforcement agent, and the nanocomposite membrane exhibited the highest tensile strength at ANFs content of 4.0 wt%. Besides the excellent tensile strength, transparency and flexibility, the surface wettability of the ANFs/BC decreased compared to that of pristine BC, indicating a relative stability in humidity. These results showed that the ANFs/BC nanocomposite membrane is strong, transparent and flexible, thus making it an excellent candidate for electronic substrates and optical materials.