The development of highly sensitive and selective uranyl ion (UO22+) probes has attracted significant attention owing to the threat to human health caused by high toxicity, radioactivity, and long half‐life. Herein, the development of aggregation‐induced emission (AIE) active polymer dots (Pdots) is described for an accurate UO22+ monitoring using a portable electrochemiluminescence (ECL) system. An AIE‐active polymer containing tetraphenylethene and boron ketoiminate moieties is prepared into Pdots and modified with ssDNA to capture UO22+, which can amplify the ECL signal of the Pdots through a resonance energy transfer mechanism. This probe provides an ultralow detection limit of 10.6 pm/2.5 ppt, which is at least two orders of magnitude lower than the known UO22+ luminescent probes. Only UO22+ can provide an obvious ECL enhancement among the various metal ions, indicating the excellent selectivity of this probe. Furthermore, a portable ECL analyzer is designed to realize UO22+ measurements in the wild. The anodic ECL mechanism of UO22+ is discovered and ECL technology is first applied in monitoring radioactive substances. This study provides a novel strategy for the development of accurate UO22+ probes and a practical UO22+ monitoring method, indicating its potential application in the environmental and energy fields. A strategy is developed for the application of accurate trace UO22+ monitoring in the wild in both the energy and environmental fields. An ultralow limit of detection of 10.6 pm/2.5 ppt and high selectivity toward UO22+ is given in this study by using a portable electrochemiluminescence system and aggregation‐induced emission‐active polymer dot based “turn on” probe.