The present disclosure relates to protein molecules that specifically bind to CD3, which may have at least one humanized CD3-binding domain. Such molecules are useful for the treatment of cancer. The protein molecule binding to CD3 may have a second binding domain that binds to another target. In one embodiment, multispecific polypeptide molecules bind both tumor antigen-expressing cells and the CD3 subunit of a T-cell receptor complex on T-cells to induce target-dependent T-cell cytotoxicity, activation, and proliferation. The disclosure also provides pharmaceutical compositions comprising the CD3-binding poypeptide molecules, nucleic acid molecules encoding these polypeptides and methods of making these molecules.