We report a flexible paper transistor made with single-walled carbon nanotubes covalently bonded cellulose (SCBC) composite without any additional semiconducting layer. Single-walled carbon nanotubes are covalently grafted to cellulose fibrils in a regenerated cellulose film to form the SCBC composite followed by a mechanical stretching process. The SCBC transistor shows a remarkable current-voltage characteristic depending on the stretching ratio. We found that the alignment of covalently bonded carbon nanotube plays a role that governs the electrical channel behavior of the SCBC composite. (C) 2013 Elsevier B. V. All rights reserved.