A virtual reality system includes a head-mounted display (HMD) having one or more facial sensors and illumination sources mounted to a surface of the HMD. For example, the facial sensors are image capture devices coupled to a bottom side of the HMD. The illumination sources illuminate portions of a user's face outside of the HMD, while the facial sensors capture images of the illuminated portions of the user's face. A controller receives the captured images and generates a representation of the portions of the user's face by identifying landmarks of the user's face in the captured images and performing other suitable image processing methods. Based on the representation, the controller or another component of the virtual reality system generates content for presentation to the user.