Thiol-reactive Michael acceptors are commonly used for the formation of chemically crosslinked hydrogels. In this paper, we address the drawbacks of many Michael acceptors by introducing pyridazinediones as new crosslinking agents. Through the use of pyridiazinediones and their mono- or di-brominated analogues, we show that the mechanical strength, swelling ratio, and rate of gelation can all be controlled in a pH sensitive manner. Moreover, we demonstrate that the degradation of pyridazinedione-gels can be induced by the addition of thiols, thus providing a route to responsive or dynamic gels. We anticipate that our results will provide a valuable and complementary addition to the existing toolkit of crosslinking agents, allowing researchers to tune and rationally design the properties of biomedical hydrogels.