Alkyl nickel intermediates relevant to catalytic processes often feature agostic stabilization, but relatively little is known about the situation in oligonickel systems. The dinickel(I) complex K[LNiI2], which is based on a compartmental pyrazolato-bridged ligand L3- with two β-diketiminato chelate arms, or its masked version, the dihydride complex [KL(NiII-H)2] that readily releases H2, oxidatively add methyl tosylate to give diamagnetic [LNiII2(CH3)] (1) with d(Ni···Ni) ≈ 3.7 Å. Structural characterization shows that the methyl group in 1 is bound to one NiII and exhibits an intramolecular agostic interaction with the more distant NiII. This is supported spectroscopically (viz., a ν(C-H) stretch at 2658 cm-1 and lowered 1JC-H of 114 Hz) and by DFT calculations, including topological analysis of the computed electron density for 1. NMR spectroscopy reveals very fast hopping of the CH3 group between the two NiII ions, which according to DFT has a minute barrier of 4 kcal mol-1 and proceeds via a planar CH3 moiety in the transition state (Walden-like inversion). The alkylidene group in K[LNi2(μ-CHSi(Me3)3)], obtained from the reaction of [KL(Ni-H)2] with N2CHSiMe3, is symmetrically bridging. This work provides new insight into the stabilization and dynamics of alkyl ligands at dinickel sites with a constrained metal···metal distance.