A bisubstrate inhibitor of Src kinases, having a nucleotide or N-heteroaromatic moiety; and a peptide/phosphopeptide, peptidomimetic, or phosphopeptide mimic moiety. The moieties are linked by a rigid or a flexible linker. The nucleotide or N-heteroaromatic moiety is ATP, ATP-mimics, N-heteroaromatics including purine-based derivatives, pyrimidine-based derivatives such as 2,4-diamino-5-substituted pyrimidine derivatives, pyrazole[3,4-d]pyrimidine derivatives, pyrrolo[2,3-d]pyrimidine derivatives, pyrido[2,3-d]pyrimidine derivatives, amino-substituted dihydropyrimido[4,5-d]pyrimidinone derivatives, thieno- and furo-substituted derivatives, quinazoline derivatives, and quinoline derivatives, and several natural products such as aminogenistein. The phosphopeptide mimics comprise phosphonate-based phosphotyrosine mimetics such as phosphonomethylphenylalanine (Pmp) and its analogues, carboxylic acid-based phosphotyrosine mimetics such as malonyltyrosine or phenylalanine analogues and their derivatives such as carboxymethyl phenylalanine, uncharged pTyr mimetics, and conformationally constrained peptides. The phosphopeptide or phosphopeptide mimics inhibits the Src kinases SH2 domain.