The 3ω technique and time-domain thermoreflectance (TDTR) are two experimental methods capable of measuring the cross-plane thermal conductivity of thin films. We compare the cross-plane thermal conductivity measured by the 3ω method and TDTR on epitaxial ( In _0.52 Al _0.48)_x( In _0.53 Ga _0.47)_1-x As alloy layers with embedded ErAs nanoparticles. Thermal conductivities measured by TDTR at low modulation frequencies (∼1 MHz ) are typically in good agreement with thermal conductivities measured by the 3ω method. We discuss the accuracy and limitations of both methods and provide guidelines for estimating uncertainties for each approach.