We introduce a facile method to fabricate geometry-controllable, high-aspect-ratio (AR approximately 10) polymer nanofibrillar structures in the form of stooped or crispated nanohairs by molding and oblique electron beam irradiation. The geometry of polymer nanohairs can be precisely tunable by controlling the tilting angle of the electron beam, the acceleration voltage, and the exposure time. This method provides a simple and versatile route to fabricating various nanofibrillar structures without a multistep process and may have applications in the fields of actuators or biomimetic attachment such as gecko-like adhesive and nano-Velcro.