The paper presents performance and modeling of the first thermally excited GaAs cantilever-based microactuator fully compatible with GaAs-based monolithic microwave integrated circuits (MMICs). The introduced microactuator shows a high electro-mechanical conversion efficiency (Γ E < space>=0.802 μm mW - 1 ) and a fast time response (τ~1.4 ms), which corresponds closely to value predicted from the thermal simulation. The typical measured resonant frequency of the microactuator is 15.4 kHz. The simulated and measured microactuator conversion characteristics are compared, indicating viability of the modeling method used for further micromechanical analyses.