An adjustable bimini bracket is for use in connection with a boat having a railing tubular member on either side of the boat, and a bimini having strut tubular members. Left and right side plates are generally parallel and spaced apart. A transverse plate extends between the side plates. Ridges are disposed intermediate the transverse plate and the end. The side plates have a pair of collinear holes therethrough adjacent each end. The bimini bracket will slidingly engage the tubular member between the side plates. A bolt and a hand knob engage the first holes. The hand knob will be tightened, clamping the tubular member between the side plates, thereby preventing the bimini bracket from sliding on the tubular member. A second bolt and a nut engage the second holes for pivotal fastening of a strut tubular member to the bimini bracket, and for fastening a tie-down. The side plates taper upward in thickness from one end to the ridges. A plurality of ribs reinforces the side plates.