Wearable　strain　sensors　are　arousing　increasing　research　interests　in　recent　years　on　account　of　their　potentials　in　motion　detection,　personal　and　public　healthcare,　future　entertainment,　man–machine　interaction,　artificial　intelligence,　and　so　forth.　Much　research　has　focused　on　fiber-based　sensors　due　to　the　appealing　performance　of　fibers,　including　processing　flexibility,　wearing　comfortability,　outstanding　lifetime　and　serviceability,　low-cost　and　large-scale　capacity.　Herein,　we　review　the　latest　advances　in　functionalization　and　device　fabrication　of　fiber　materials　toward　applications　in　fiber-based　wearable　strain　sensors.　We　describe　the　approaches　for　preparing　conductive　fibers　such　as　spinning,　surface　modification,　and　structural　transformation.　We　also　introduce　the　fabrication　and　sensing　mechanisms　of　state-of-the-art　sensors　and　analyze　their　merits　and　demerits.　The　applications　toward　motion　detection,　healthcare,　man–machine　interaction,　future　entertainment,　and　multifunctional　sensing　are　summarized　with　typical　examples.　We　finally　critically　analyze　tough　challenges　and　future　remarks　of　fiber-based　strain　sensors,　aiming　to　implement　them　in　real　applications.[Figure　not　available:　see　fulltext.]　©　2022,　The　Author(s).