The proto-oncogene tyrosine-protein kinase Src is a key element of signaling cascades involved in the invasive and metastasis-forming capacity of cancer cells. While membrane tyrosine-kinase receptors are known to dimerize, Src is classified as a non-receptor kinase and assumed to remain always monomeric. Here we demonstrate the formation of stable dimers by the first domains of myristoylated Src previously shown to be sufficient for Src trafficking. Src dimers fused to green fluorescent protein (GFP) on supported lipid bilayers were identified using single-molecule photobleaching experiments. Competition with a protein containing only native Src domains without GFP confirms that dimerization is a previously overlooked intrinsic property of Src. Dimerization is concomitant to membrane binding by the myristoylated forms of Src and may constitute a new regulation layer for the Src oncogene.