Adhesively bonded joints are used extensively in modern aerospace vehicles and composite design. However, their failure behavior is not well understood. Therefore, joints are often overdesigned to compensate for uncertainties in order to prevent premature failure. Previous studies have demonstrated the applicability of the digital image correlation (DIC) technique to investigate the strain field in composite lap joint specimens. This study extends the use of DIC analysis to investigate Mode I failure in adhesively bonded Double Cantilever Beam (DCB) specimens having a pre-existing blunt or a sharp debond. The DIC experimental setup enabled the visualization of crack initiation and growth in the adhesive, adhesive/laminate interface, and within the composite laminate.