As the aromatic tryptophan (Trp) side chain plays a pivotal role in influencing the structure and function of peptides and proteins, it has become an attractive target for the late‐stage modification of these important biomolecules. Herein, we report an electrochemical approach for late‐stage functionalization of peptides containing a Trp side chain through manganese‐catalyzed tandem radical azidation/heterocyclization. This electrochemical oxidative strategy provides access to azide‐substituted tetrazolo1,5‐aindole‐containing peptides with broad functional group tolerance, high site selectivity, and good yields of products (up to 87 %) under mild buffer conditions. Moreover, the modified Trp‐containing peptides bearing an azide functionality are promising building blocks, paving the way for the construction of various derivatives, such as “click” chemistry products. Manganese‐catalyzed late‐stage derivatization was used to construct azide‐substituted tetrazolo1,5‐aindole‐containing peptides through a radical azidation/heterocyclization cascade. This electrochemical oxidative strategy could be conducted under mild, efficient, and environmentally friendly conditions in buffer solution.