The late-stage diversification (LSD) of structurally complex peptides has emerged as a powerful platform for molecular engineering and drug discovery. Besides traditional peptide modifications, such as native chemical ligations or cross-couplings with prefunctionalized substrates, during recent years, C―H activation has gained considerable momentum as a robust and step-economical strategy for late-stage peptide modifications, thus far predominantly for the formation of C―C bonds. Although C―N bond formations represent established strategies in medicinal chemistry and drug discovery, methods for direct amidations of tryptophan and tryptophan-containing peptides are rare and severely limited to the activated C2 position. In contrast, we herein disclose the first example of direct late-stage peptide C―H amidation reaction and the unprecedented late-stage peptide diversification on tryptophan C7 position in a highly site-selective manner. Moreover, this strategy sets the stage for sequential double C(7)―H/C(2)―H modifications, further improving the peptide structural complexity. © 2020 Elsevier Inc. Peptides represent biopolymers of key relevance to biochemistry, medicinal chemistry, natural product synthesis, and pharmaceutical industries, among others. Traditional peptide syntheses thus far largely relied on lengthy functional group interconversions. Resource-economic C–H activation has surfaced as a transformative platform for peptide modifications but continues to be restricted to tryptophan modifications at the C2-position. In sharp contrast, C7-selective peptide modifications have now been realized by versatile rhodium catalysis. The catalyzed C–H amidations occurred with outstanding levels of C7 site selectivity on highly functionalized peptides. These findings unravel the unique potential of biorthogonal late-stage diversification for the direct assembly of structurally complex peptides for biology, molecular syntheses, and drug discovery. © 2020 Elsevier Inc. Herein, we disclose the first late-stage peptide C–H nitrogenations through unprecedented rhodium(III)-catalyzed peptide C7 diversification. Thus, peptides were directly transformed through position-selective C7 amidations with easily accessible 1,4,2-dioxazol-5-ones. Structurally complex peptides featuring a wealth of functional groups underwent C7-C–H amidations to deliver selectively modified natural product and drug hybrids. © 2020 Elsevier Inc.