The present invention relates to anti-claudin 1 antibodies and their uses thereof. In particular, the present invention relates to an anti-Claudin 1 (CLDN1) antibody comprising n heavy chain variable region comprising SEQ ID NO:2 in the H-CDR1 region, SEQ ID NO:3 in the H-CDR2 region and SEQ ID NO:4 in the H-CDR3 region and a light chain variable region comprising SEQ ID NO:6 in the L-CDR1 region, SEQ ID NO:7 in the L-CDR2 region and SEQ ID NO:8 in the L-CDR3 region.