An easy-installable bracket for retaining a bed mattress is provided. The bracket is adapted to be disposed on a bed frame having a head portion and a feet portion. The bracket includes two seats and a bracket member. Each of the seats has a bottom plate for fixed at the feet portion of the bed frame, and an arcuate portion extended from the bottom plate. Two passages are respectively defined between the arcuate portions of the seats and the feet portion. The bracket member has a vertical portion, two front-extending sections respectively extended from two bottom ends of the vertical portion toward the head portion of the bed frame, and two parallel rear-extending sections respectively extended from distal ends of the front extending sections toward the feet portion. The rear-extending sections are slidably received in the passages respectively.