Cleavage and formation of the O‒O bond in dioxygen is among the most important metal‐dependent processes in Nature. The former process has been mimicked structurally and functionally with a number of biomimetic iron complexes. The reverse process, namely the dioxygen bond formation, however, appears unfavorable with iron. Over the years many attempts have been made to oxidize water on a mononuclear iron center through reactions with peroxide. In this work we present a computational study focused on the mechanism of dioxygen formation on two mononuclear non‐heme iron(IV)‐oxo species upon addition of peracid (m‐chloroperbenzoic acid, mCPBA). A range of test reactions and sequences are analyzed with thermochemical cycles with respect to the thermodynamic and kinetic feasibility of product formation. The work shows that iron‐borne O‒O bond formation through peracid attack at FeIVO indeed is feasible through two competing pathways. These are initiated by homolytic inner‐sphere splitting of the RC(O)OO‐H and the RC(O)O‐OH bond in the peracid, respectively.