A selectorized dumbbell includes a horizontal stack of nested left weight plates and a horizontal stack of spaced right weight plates with the stacks being separated by a gap into which a handle may be inserted. A selector is movable into different positions relative to the handle to vary how many nested left and right weight plates from the stacks thereof are coupled to the handle to vary the exercise mass of the handle. Each left weight plate has a counterpart right weight plate counterpart which are coupled together by at least one interconnecting member having a first keyhole slot connection between the left end of the interconnecting member and the left weight plate and a second keyhole slot connection between the right end of the interconnecting member and the right weight plate.