The present invention provides compositions and methods of use of humanized, chimeric or human Class I anti-CEA antibodies or fragments thereof, preferably comprising the light chain variable region CDR sequences SASSRVSYIH (SEQ ID NO:1); GTSTLAS (SEQ ID NO:2); and QQWSYNPPT (SEQ ID NO:3); and the heavy chain variable region CDR sequences DYYMS (SEQ ID NO:4); FIANKANGHTTDYSPSVKG (SEQ ID NO:5); and DMGIRWNFDV (SEQ ID NO:6). The Class I anti-CEA antibodies or fragments are useful for treating diseases, such as cancer, wherein the diseased cells express CEACAM5 and/or CEACAM6 antigens. The Class I anti-CEA antibodies or fragments are also of use for interfering with specific processes, such as metastasis, invasiveness and/or adhesion of cancer cells, or for enhancing sensitivity of cancer cells to cytotoxic agents and have favorable effects on the survival of subjects with cancer.