Triple negative breast cancer (TNBC) is characterized by an aggressive biologic behavior without specific targeted agent. Nicotinamide has recently been proven as a novel therapeutic agent for skin tumors in ONTRAC trial. Here we performed in-depth proteomes to characterize network of molecular interactions in TNBC cells treated by nicotinamide. Proteome profiles identified nicotinamide drives significant functional alterations related to major cellular pathways, including cell cycle, DNA replication, apoptosis and DNA damage repair. We further elaborated global signaling networks of molecular events with nicotinamide inducible expression changes in protein levels. This approach reveals that nicotinamide treatment rewires signaling networks towards dysfunction of DNA damage repair and away form a pro-growth state in TNBC. To our knowledge, our results of high resolution signaling network interactions provides the first evidence to comprehensively support the hypothesis of nicotinamide as a novel therapeutic agent in TNBC.