Gibberellins (GAs) modulate diverse developmental processes throughout the plant life cycle. However， the interaction between GAs and the circadian rhythm remains unclear. Here， we report that MUT9p-LIKE KINASE1 (MLK1) and MLK2 mediate the interaction between GAs and the circadian clock to regulate hypocotyl elongation in DELLA proteins function as master growth repressors that integrate phytohormone signaling and environmental pathways in plant development. MLK1 and MLK2 interact with the DELLA protein REPRESSOR OF (RGA). Loss of and function results in plants with short hypocotyls and hyposensitivity to GAs. MLK1/2 and RGA directly interact with CIRCADIAN CLOCK ASSOCIATED1 (CCA1)， which targets the promoter of () to regulate its roles in cell expansion. MLK1/2 antagonize the ability of RGA to bind CCA1， and these factors coordinately regulate the expression of RGA suppressed the ability of CCA1 to activate expression from the promoter， but MLK1/2 reversed this suppression. Genetically， act in the same pathway as and in hypocotyl elongation. Together， our results provide insight into the mechanism by which MLK1 and MLK2 antagonize the function of RGA in hypocotyl elongation and suggest that MLK1/2 coordinately mediate the regulation of plant development by GAs and the circadian rhythm in Arabidopsis.