Metallothionein‐3, also called neuronal growth‐inhibitory factor, is one of the four members of the mammalian metallothionein family, which in turn belongs to the metallothionein, a class of ubiquitously occurring low‐molecular‐weight cysteine‐ and metal‐rich proteins containing metal–thiolate clusters. Mammalian metallothioneins contain two metal–thiolate clusters of the type M(II)3‐Cys9 and M(II)4‐Cys11 [or Cu(I)4‐CysS6‐9]. Although metallothionein‐3 shares these metal clusters with the well‐characterized metallothionein‐1 and metallothionein‐2, it shows distinct biological, structural and chemical properties. This short review focuses on the recent developments regarding the chemistry of the metal clusters in metallothionein‐3, in comparison to those in metallothionein‐1 and metallothionein‐2, and discusses the possible biological and functional implications.