Provided herein are anti-LAP antibodies (e.g., recombinant humanized, chimeric, and human anti-LAP antibodies) or antigen binding fragments thereof which have therapeutically beneficial properties, such as binding specifically to LAP-TGFβ1 on cells but not to LAP-TGFβ1 in extracellular matrix, as well as compositions including the same. Also provided are uses of these antibodies or antigen binding fragments in therapeutic applications, such as in the treatment of cancer, and diagnostic applications.