The [Rh₂(OAc)₄]‐catalyzed decomposition of {[(4‐nitrophenyl)sulfonyl]imino}phenyl‐λ³‐iodane (NsN=IPh) resulted in formal insertions into CH bonds, activated by phenyl or vinyl groups, or by O‐substituents. Scope and limitations of the reaction were investigated. Yields of up to 84% were achieved in the most favorable cases. Yields were enhanced by electron‐releasing substituents and decreased by steric hindrance. Aziridination competed with allylic insertion with olefinic substrates. The insertion reaction proceeded with retention of configuration. With chiral RhII catalysts, a modest asymmetric induction was observed. A mechanism involving direct insertion by a Rh‐complexed nitrene into the CH bond is proposed.