Diamond (Dia) films are promising heat-dissipative materials for electronic packages since they combine high thermal conductivity with high electrical resistivity. However, precise knowledge of the thermal properties of the diamond films is crucial to their potential application as passive thermal management substrates in electronics. In this study, modulated photothermal radiometry (MPTR) in a front-face configuration was employed to thermally characterize polycrystalline diamond films deposited onto silicon (Si) substrates through laser-assisted combustion synthesis. The intrinsic thermal conductivity of diamond films and the thermal boundary resistance (TBR) at the interface between the diamond film and the Si substrate were investigated. The results enlighten the correlation between the deposition process, film purity, film transverse thermal conductivity, and interface thermal resistance.