© The Royal Society of Chemistry 2020. Recent developments in miniaturized electronic devices with sophisticated computational capabilities and remarkably low power communication technologies involve a tendency toward powering these devices with long cycle life, high energy efficiency, fast and cheap production and lightweight power sources. Integration of piezoelectric materials and novel fabrication techniques with conventional textile processes established the emergence of a wearable technology field which can fulfill this purpose. Mechanical energy harvesters are required for multiple applications such as structural health monitoring systems, self-powered wireless sensors, and harvesting energy from body movements inexpensively. Among the variety of materials exhibiting piezoelectricity, polymers are more considered due to their many excellent properties desirable in flexible piezoelectric generators. Hence, fiber-based electronic devices have the best features for human garments such as flexibility, stretchability, permeability and lightweight, and they are ideal interface platform options between the environment, electronic devices and human body. Hence, this article starts with the fundamentals of wearable technology and materials involved and then reviews recent developments in fiber-based self-powered systems and sensors with the special focus on the piezoelectric poly(vinylidene fluoride) polymer and barium titanium oxide ceramic. In addition, a number of strategies that may improve the piezoelectric generator performance are summarized. Furthermore, the global textile market industry and the high-performance end-user such as washability and durability were reviewed. Potential difficulties, challenges and opportunities in the field of fiber-based energy generators are also explored.