The wide use of acetylacetone (Acac) in industries is fueling the need for the development of Acac detection methods. However, only a few nanomaterial-based fluorescent probes for Acac have been reported, and these probes either lack turn-on detection capability, and/or aqueous compatibility. Herein, a series of iridium(III) dimers were synthesized in one step and screened as luminescent probes for Acac. The candidate probe 8 exhibited a luminescence enhancement of near 160-fold in the presence of Acac in aqueous solution, with a linear relationship of Acac (0.1–10 μM) and a limit of detection (LOD) of 0.043 μM. Mechanistically, the probe chelated with Acac to form a new luminescent complex. Moreover, the long lifetime of probe 8 allowed its response to Acac to be distinguished from fluorescent interference through time-resolved emission spectroscopy (TRES). Probe 8 further demonstrated its practical application as a luminogenic probe for Acac in real water samples. In summary, because probe 8 is very easily prepared and modified compared with existing Acac luminescence probes, it serves as an ideal starting point to develop next-generation luminogenic probes for monitoring Acac in environmental and biological systems.