A variable-gap silicon nanowire waveguide coupler was fabricated and its characteristics were measured for comparison with those determined by a rigorous electromagnetic simulation. The three-dimensional model of the coupler was simulated by the finite-difference time-domain method. On the basis of the results obtained, a compact 1× 3 silicon nanowire coupler switch was designed and fabricated. The 1× 3 switch was composed of two couplers with parallel silicon nanowire waveguides of 400nm width and 260nm thickness and comb-drive electrostatic actuators. The output isolation and extinction ratio of the variable coupler were measured to be 12.9 and 18.6 dB, respectively. The loss of the variable coupler was 0.21 dB. The measured coupling coefficient was explained quantitatively by the simulation. The proposed 1 × 3 switch was demonstrated by showing the infrared images of the switch outputs. The port isolation of the 1 × 3 switch was better than 11.3 dB.