Multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) is a powerful technique for the study of biogeochemical cycling of a variety of metals. The advantages of this technique include high ionization efficiency, low detection limits, and rapid analysis. It can produce highly precise and accurate elemental isotope compositions of natural and experimental samples, which can provide insights into the mechanisms of both biological and abiological processes in in natural environments. In this chapter, the operating principles of the instrument, purification of samples, interferences encountered, correction methods to eliminate the instrumental mass discrimination, and data analysis with respect to reliability and reproducibility are discussed. A case study is included that highlights the capability of MC-ICP-MS to infer mechanisms of Fe redox processes in an acidic oligotrophic lake using natural abundance of stable Fe isotopes.