The direct construction of chiral 1,2-diamines through the stereoselective functionalization of two vicinal C(sp3)─H bonds remains a significant synthetic challenge. We report an iron-catalyzed, carboxylate-directed asymmetric vicinal α,β-C(sp3) ─H diamination of readily available carboxylic acids that furnishes chiral α,β-diamino acids in a single pot with high regio-, diastereo-, and enantioselectivity (up to >20:1 dr and >99% ee). Using a chiral tetradentate N4-ligated Fe(II) catalyst and BocNHOMs as the aminating reagent, a broad range of aromatic and aliphatic substrates undergo two sequential, nitrene-mediated C─H aminations under mild conditions. Mechanistic studies indicate stepwise amination via iron−nitrenoid species, where the initial site of hydrogen-atom transfer (β for aromatic substrates, α for aliphatic ones) dictates the order of functionalization. The method tolerates diverse functional groups and operates enantioconvergently for selected racemic substrates. This sustainable iron-catalyzed strategy enables direct conversion of abundant carboxylic acids into versatile chiral α,β-diamino building blocks amenable to peptide synthesis and heterocycle formation.