Disclosed are CD70 binding agents, such as humanized anti-CD70 antibodies and fragments and derivatives, that exert a cytotoxic, cytostatic or immunomodulatory on CD70 expressing cells, as well as pharmaceutical compositions and kits comprising the antibody, fragment or derivative. Also disclosed are methods for the treatment of CD70-expressing cancers and immunological disorders, comprising administering to a subject the CD70 binding agents or pharmaceutical compositions.