Compared to plant cellulose, bacterial cellulose synthesized by Gluconacetobacter xylinus has features such as high crystallinity, tensile strength and water absorption capacity; biocompatibility; resistance to degradation and low solubility that may be advantageous for engineered tissue. However, little information is available concerning the potential toxicity of bacterial cellulose-based biomaterials. The present study investigated the toxicity of bacterial cellulose nanofibers in vitro in human umbilical vein endothelial cells (HUVECs) using viability and flow cytometric assays and in vivo using C57/Bl6 mice. The absence of toxicity in vitro and in vivo supports the view that bacterial cellulose may be amenable for use as a tissue engineering biomaterial.