Nature uses mechanochemical transduction processes to achieve diverse and vital functions, such as hearing, cellular adhesion and gating of ion channels. One fascinating example of biological mechanotransduction is the emission of light on mechanical stimulation. However, molecular-level transduction of force into luminescence in a synthetic system remains a challenge. Here, we show that bis(adamantyl)-1,2-dioxetane emits visible light when force is applied to a polymer chain or network in which this unit is incorporated. Bright-blue luminescence was observed on sonication of solutions of dioxetane-containing linear polymers and on the straining of polymer networks with dioxetane crosslinkers. Light is emitted from the adamantanone-excited state that forms on opening of the four-membered dioxetane ring. Increased sensitivity and colour tuning were achieved by energy transfer to suitable acceptors. High spatial and temporal resolutions highlight the potential to study the failure of polymeric materials in unprecedented detail.