Iron is an important trace metal in oceans, and its concentrations greatly influence primary productivity, carbon cycling, and global climate change. Submarine hydrothermal venting is an important source of dissolved iron in global oceans and has been widely discussed in marine science. The iron isotopes of hydrothermally sourced Fe are different from those of the surrounding seawater and can be used as a potential tracer for their distribution and migration in the oceans. Previous studies on Fe speciation and isotopes in hydrothermal processes have been reviewed herein. We summarize the iron species in hydrothermal plumes, including organic, colloidal, and particulate iron; the processes influencing iron isotope fractionation; and the characteristics of iron isotopes in hydrothermal plumes. Finally, the key scientific issues that should be highlighted in future studies are presented.