We present microcantilevers that utilize magnetic actuation for use as mass sensors for bioapplications. The microcantilevers are made of electroplated cobalt–nickel that has low coercivity and high saturation magnetization. The microcantilevers are actuated by applying magnetic fields, and the deflection is measured using a laser Doppler vibrometer. The microfabrication of the microcantilevers is based on two lithography steps, an electroplating step and a sacrificial layer etching step. The magnetic actuation and optical readout using the fabricated cobalt–nickel microcantilever were successfully demonstrated in air under atmospheric pressure and in deionized water. A feedback circuit is used to enhance the quality factor of the microcantilever. The quality factor increased from approximately 550 to 1600 in air and from 7.3 to 10.6 in deionized water. The microcantilevers can be readily functionalized with selective binding molecules and used as a biomass sensor.