T cell receptors (TCRs) that have specificity for the WT1 antigen are provided. The TCRs include higher affinity TCRs that were engineered through the generation of mutational libraries of TCRs in a single-chain format, followed by selection for improved stability and affinity on the surface of yeast (i.e. directed evolution). In embodiments, the TCRs can be used in soluble form for targeted delivery in vivo, or as genes introduced into T cells in an adoptive T cell setting.