Surgical tissue fasteners and related deployment systems and methods are disclosed. A tissue fastener used to join multiple tissue layers includes a first member, a second member, and a connecting member connecting the first and second members. In some embodiments, the first and second members are configured to expand from a delivered state to a deployed state in which the fastener secures the tissue layers together. Other tissue fastener embodiments include means for applying a substantially constant force on the tissue layers and/or means for adjusting a length of the connecting member between the first and second members.