Small-molecule based fluorescent probes for Hg2+, Pb2+ and Cd2+ since 2003 concluded in this review. Display omitted •Probes to detect toxic metal ions focused on Hg2+, Pb2+ and Cd2+ ions.•Fluorescent probes are subdivided according to sensing mechanism.•Reaction-based probes are listed separately.•Typical examples in cells are emphasized with colorful image. Heavy-metal pollution, especially Hg2+, Pb2+ and Cd2+, have become a serious issue worldwide. Exposure to even very low concentrations of these metals will threaten human health and cause various illness. More seriously, these metals could not be biodegraded, and would gradually accumulate in environment as well as livingorganism. The development of rapid, accurate and economic methods to detect them is significant important to reduce or avoid exposure to these metals. Consequently, much effort has been dedicated to design and synthesize fluorescent probes that can selectively detect Hg2+, Pb2+ and Cd2+. Herein, we summarized recent small molecular fluorescent probes for these metals. To be helpful for rational design, these probes are divided into three types according to response modes (turn-off, turn-on, ratiometric probes) and are further subdivided according to sensing mechanism (PET, ICT, AIE and others). Especially, reaction-based probes are listed separately because of its good selectivity.