A new family of robust, non‐toxic, water‐compatible ruthenium(II) vinyl probes allows the rapid, selective and sensitive detection of endogenous carbon monoxide (CO) in live mammalian cells under normoxic and hypoxic conditions. Uniquely, these probes incorporate a viscosity‐sensitive BODIPY fluorophore that allows the measurement of microscopic viscosity in live cells via Fluorescence Lifetime Imaging Microscopy (FLIM) in conjunction with measuring CO. This is the first example of a probe that can simultaneously detect CO alongside small viscosity changes in organelles of live cells.