Temperature-dependent magnetization, specific heat, and magnetic field modulated microwave spectroscopy (MFMMS) measurements were performed on single crystals of KxFeSe2. Magnetization measurements yield a superconducting transition temperature (Tc) of ∼30 K, with a diamagnetic shielding fraction of nearly 90%. Specific heat measurements revealed a 'jump' at Tc, , of about 6.8 ± 1 mJ mol−1 K−2, consistent with bulk superconductivity in KxFeSe2. Moreover, MFMMS measurements detect the superconductivity of KxFeSe2 with a peak with an onset at ∼ 28 K, close to the values of Tc determined from the magnetization and specific heat measurements. The presence and the shape of the low temperature MFMMS signal could be ascribed to a complex dissipation mechanism and percolative superconductivity.