As an emerging revolutionary technology, smart wearables can be directly worn on the body; integrated into clothes; and exhibit desirable characteristics, including light weight, portability, softness and natural conformity to the curved human body surface. Because of the high air permeability, compatibility with the human body, and wear comfort of textiles, the seamless integration of the smart wearable technology with textiles is regarded as the future direction for essential development. The use of fiber electronics as building units to weave smart wearable textiles can not only endow traditional clothes with multiple intelligent functions and wearable systems with ideal breathability, but can also provide endurance to modern textile processing technologies such as knitting and weaving, which opens up a brand-new path for the large-scale application of wearable electronics. This review comprehensively summarizes the state-of-the-art advancements in smart wearable fibers and textiles, including smart materials, properties, fabrication strategies, surface modifications, and smart wearable applications. We focus on advanced smart wearable fibers and textiles, which could simultaneously exhibit excellent multi-functions and highly comfortable wearable experience even under large mechanical deformations, and discuss the strategies and mechanisms that are suitable for fabricating smart wearable fibers and textiles with excellent signal capture and transmission reliability. Finally, a critical discussion of the opportunities and challenges associated with smart wearable fibers and textiles towards practical wearable applications is presented.