In this paper, we present the implementation of a novel structure of a double-pole-double-throw (DPDT) switch with eighth-wavelength transmission lines. The switch consists of eight diodes, eight eighth-wavelength transmission lines, and four frequency-optimized matching lines. It can be used as a single-pole-double-throw (SPDT) switch when one of the ports is terminated with a characteristic impedance of 50 Ω to the ground. By using eighth-wavelength transmission lines, the isolation of the switch is highly improved. The performance characteristics of the traditional quarter-wavelength SPDT and DPDT have also been evaluated for comparison with the proposed design. Measured results show that the insertion loss reaches a value as high as 1.65 dB, and the isolation is 30 dB at a frequency of 2.4 GHz. The size of the switch is nearly the same as that of the conventional quarter-wavelength DPDT switch. This novel switch can be used in wireless sensor applications.