Specific heat (SH) measurements of RMn2Hx (R=Y, Ho; x=0–4.3) powders have been performed by a quasi-adiabatic (in the temperature range of 50–320K) and relaxation (2–400K) methods. The hydrogenation causes a large increase of the transition temperature TN with the enhancement of both SH peaks at TN and the specific heat background. Various features of the double specific-heat anomaly were observed close to TN. The possible correlations between the hydrogen vibration modes, hydrogen migration, and the specific heat anomalies have been discussed.