Nonphotochemical quenching (NPQ) is an important photoprotective mechanism that quickly dissipates excess light energy as heat. NPQ can be induced in a few seconds to several hours; most studies of this process have focused on the rapid induction of NPQ. Recently, a new, slowly induced form of NPQ, called qH, was found during the discovery of the quenching inhibitor suppressor of quenching 1 (SOQ1). However, the specific mechanism of qH remains unclear. Here, we found that hypersensitive to high light 1 (HHL1)—a damage repair factor of photosystem II—interacts with SOQ1. The enhanced NPQ phenotype of thehhl1mutant is similar to that of thesoq1mutant, which is not related to energy-dependent quenching or other known NPQ components. Furthermore, thehhl1 soq1double mutant showed higher NPQ than the single mutants, but its pigment content and composition were similar to those of the wildtype. OverexpressingHHL1decreased NPQ inhhl1to below wildtype levels, whereas NPQ inhhl1plants overexpressingSOQ1was lower than that inhhl1but higher than that in the wildtype. Moreover, we found that HHL1 promotes the SOQ1-mediated inhibition of plastidial lipoprotein through its von Willebrand factor type A domain. We propose that HHL1 and SOQ1 synergistically regulate NPQ.