For the first time, we studied the static and dynamic mechanical response of CNT forests under electrostatic loading. Apparent stiffening of the CNT forests after cyclic loading is attributed to morphological change of straightening of the individual CNTs at the top of the pillar in which the electric field penetrates, along with relaxation of residual strains accumulated during the growth pro- cess. Unlike common solid materials such as silicon that are used in NEMS/MEMS devices, CNT forests are much softer and exhibit significant energy dissipation due to internal damping by stick-slip of CNT contact sites. The low stiffness and wide bandwidth of CNT forests under resonance may suggest their use as soft resonant elements that measure small forces over large contact areas, or that electrostatically detect changes in surface conditions of CNTs such as adsorption of molecular species. Thorough understanding of those properties will enable new applications that leverage the capability to design and fabricate CNT forest patterns using con- ventional lithography and CVD methods.