An optoisolator leadframe assembly includes: an emitter leadframe part including a first rail and a plurality of emitter leadframe units, each rail including two rows of emitter leadframes, each having a die-mounting pad; and a receiver leadframe part including a second rail and a plurality of receiver leadframe units, each including two rows of receiver leadframes, each having a die-mounting pad. The die-mounting pads of the emitter leadframes of each row of each of the emitter leadframe units are respectively aligned with and spaced apart from the die-mounting pads of the receiver leadframes of an adjacent row of an adjacent one of the receiver leadframe units. Each of the emitter and receiver leadframe parts is a single piece.