The oxidation of manganese complexes using ceric ammonium nitrate (CAN) is often complicated by the fact that cerium(IV) can serve as both an oxidant and a Lewis acid. In this work, we explore the reaction of CAN with the MnII complex [MnII(OTf)(DMMN4py)](OTf) (DMMN4py = N,N-bis(4-methoxy-3,5-dimethyl-2-pyridylmethyl)-N-bis(2-pyridyl)methylamine). We chose this complex as multiple oxidation products, including oxomanganese(IV) and bis(μ-oxo)dimanganese(III,IV) complexes, have previously been reported. We envisioned that knowledge of the spectral properties of these intermediates would aid in understanding the potential complexities of CAN oxidation reactions. The oxidation of [MnII(OTf)(DMMN4py)](OTf) with 2.0 equiv CAN in 9:1 (v/v) MeCN:H2O at 25 °C transiently forms the MnIV-oxo complex, but this species is formed in low yields and is unstable. The MnIV-oxo complex evolves to a new intermediate that had not been previously observed. At lower temperatures, the formation of this new intermediate is preceded by formation of the previously reported bis(μ-oxo)dimanganese(III,IV) complex. EPR and X-ray absorption experiments for the new intermediate provide strong evidence for its formulation as [MnIVMnIV(μ-O)2(DMMN4py)2]4+. This work establishes dinuclear MnIVMnIV species as products that must be considered in CAN oxidation reactions of MnII complexes and shows that both mononuclear MnIV-oxo and dinuclear MnIIIMnIV complexes can be intermediates in such reactions.