We report on the growth and subsequent work function measurements of diamond film covered surfaces. Diamond films were grown via a thermal chemical vapor deposition technique. The feed gas mixture used was 1% CH4/99% H-2. Raman spectroscopy was used to verify diamond growth. Electron emission was investigated and work function values obtained in field emission as well as thermionic emission modes. However, we primarily report on a unique way to ascertain the absolute work function of diamond surfaces using the field emission retarding potential technique. This experimental method readily lends itself to these types of investigations where values can be determined apart from thermal or field effects. This method gives a diamond surface work function of 4.15+/-0.05 eV.