Nowadays, the demand for sustainable energy devices (e.g. lithium ion batteries, supercapacitors, solar cells) has increased rapidly in recent decades. Nanocelluloses (NCs) from plants or bacteria have shown promising potential as their excellent physical, mechanical and optical properties, which are important for fabricating high-performance energy devices. NC materials and their applications in different areas have been extensively reviewed in literature. However, those reviews focused on more broad properties and applications of NC materials but the discussion on the energy applications are far from comprehensive. Technically, NCs are not electrically conductive; however, conductivity is essential for some core components of an energy device. Therefore, various chemical or physical modification approaches have been developed to prepare conductive NC-based materials. Because of the excellent physical properties of NC materials as well as the rapidly increasing demands on renewable materials based energy devices, enormous research efforts have been devoted to the NC-based conductive materials and energy devices. This paper is a comprehensive review focusing on the recent progress of fabricating conductive NC materials and the energy devices, including supercapacitors, lithium ion batteries and solar cells.