Cellulose nanocrystals (CNC) have attracted great interest as nanoreinforcement due to their excellent mechanical properties. Furthermore, their dispersibility in water makes them suitable for their incorporation in many aqueous systems such as waterborme polyurethanes (WBPU). WBPUs have gained attention due to their versatility and ability to ajust their properties to a wide range of applications, in addition to their non-toxicity, non-flammability and environmental sustainability. Therefore, in this work a waterborne polyurethane has been synthesized for the preparation of nanocomposites with different contents of cellulose nanocrystals, incorporated by different routes, the classical mixing by sonication once the waterborne polyurethane has been synthesized, and the alternative in-situ by adding the CNCs in water during the WBPU synthesis, just in the phase inversion step. The obtained dispersions have been used in the preparation of films by casting and mats by electrospinning. The films and mats have been characterized from the point of view of their physical-chemical, morphological and superficial properties.