β-lactamase-mediated resistance to β-lactam antibiotics is an increasing threat to clinical antimicrobial chemotherapy. The combinations of β-lactam antibiotics and β-lactamase inhibitors (such as sulbactam, tazobactam and clavulanic acid) have been successfully used for overcoming class A β-lactamase-mediated resistance. However, none of the inhibitors effective against class B, C or D β-lactamases are available in the clinic, which alarms an urgent need to discover/design broad-spectrum β-lactamase inhibitors or new β-lactam antibiotics capable of evading bacterial enzymatic inactivation. In recent years, inhibitors targeted to serine β-lactamases have been developed rapidly with a few of them under clinical trials. In contrast, none promising class B β-lactamase (metallo-β-lactamase) inhibitors with good druggability have been discovered, despite the increasing number of active molecules reported. In this review, we summarized the potential β-lactamase inhibitors reported in recent years and updated the current status of β-lactamase inhibitor discovery.