The superconducting state of Ba-intercalated phenanthrene, Ba(1.5)phenanthrene, has been investigated by specific-heat measurements down to 0.4 K. A clear anomaly associated with the superconducting transition at T-c = 4.7 K indicates the bulk nature of the superconductivity. The temperature and the magnetic-field dependence of the electronic specific heat are consistent with a fully gapped superconducting order parameter. The electron-phonon coupling constant estimated from the specific-heat jump is 0.55 to 1.06, suggesting that the superconductivity of Ba1.5phenanthrene can be explained within the BCS approach with intermediate coupling mediated by phonons of approximately 100 cm(-1) in frequency, which is assigned as intercalant phonons or intermolecular phonon modes.