In this paper, the design and implementation of a low-cost planar RF MEMS-based attenuator is presented. The attenuation is realized by moving a low-resistivity silicon over a meandered grounded coplanar waveguide (GCPW) line. The actuation mechanism is achieved by magnetic forces between a planar spiral coil and a highly magnetized permanent magnet. The attenuator is designed, fabricated, and tested. An insertion loss of less than 1.20 dB and an attenuation range of 16 dB with flat response over the frequency band of 21.5–26.5 GHz are demonstrated.