Efficient detection of toxic radioiodine species emitted by nuclear-related activities and accidents is crucial for the health of the human body and safety of the environment. Herein we report that a series of stable Ln-based MOFs with BTC linkers (Ln-BTCs) could provide dual fluorescence and electrochemical response of iodine vapor in the presence of humidity. Iodine molecules could be attracted by the oxygen sites of carboxylate linkers and confined in the cavities of Ln-BTCs. Due to the photoinduced electron transfer effect, the fluorescence of Ln-BTCs is quenched drastically in the presence of iodine. Meanwhile, the conductivity of Ln-BTCs could reach an increase of 107 fold in magnitude after iodine trapping. Water molecules could also be trapped in Ln-BTCs, having interacted with the frameworks via hydrogen bonds, and reduce the iodine uptake capacity, but they cannot alter the fluorescence and conductive properties of Ln-BTCs as distinctly as iodine molecules could. Besides, Raman mapping suggests a diffusion coefficient of 1.5 × 10-14 m2 s-1 for iodine transport in the porous Eu-BTC. The dual fluorescence and electrochemical signal outputs show high sensitivity and attractive ability to reduce false positives, which could be useful for potential integration for sensing radioiodine vapor.