Dielectric properties and AC conductivity of in-situ formed AuNPs/PEGMEA/PEGDA nanocomposite film was investigated at room temperature. Frequency dependent dielectric constant shows that there are two main relaxation mechanisms for both samples. First of these mechanisms which correspond to dipolar polarization of long polymer chain was observed at frequencies between 0.1-10(3) Hz, 0.1-10(4) Hz for PEGMEA/PEGDA film and AuNPs/PEGMEA/PEGDA nanocomposite film, respectively. This mechanism has dielectric constant of 10.8, 14.1 for PEGMEA/PEGDA film and AuNPs/PEGMEA/PEGDA nanocomposite film, respectively. The second mechanism which was attributed to dipolar polarization of chain branches was observed at frequencies between 10(2)-10(6) Hz, 10(5)-10(7) Hz for PEGMEA/PEGDA film and AuNPs/PEGMEA/PEGDA nanocomposite film, respectively. This mechanism has dielectric constant of 9.6 for PEGMEA/PEGDA film and 10.3 for AuNps/PEGMEA/PEGDA nanocomposite film which cured in the presence of Irg-907 as Type I initiator by using medium pressure mercury light. These relaxation mechanisms can also be detected at frequency dependence of dielectric dissipation (tan delta) as Cole-Cole fitted relaxation peaks and of AC conductivity graphs as frequency independent (DC-like), and frequency dependent regions. DC-like region, it was thought that the main effect of AuNPs was observed, has values for AuNPs/PEGMEA/PEGDA nanocomposite film and PEGMEA/PEGDA film as 6x10(-7) and 2x10(-8) S/cm, respectively. In addition to these two polarization mechanisms, electrode polarization was observed at frequencies lower than 1 Hz for AuNps/PEGMEA/PEGDA nanocomposite film due to accumulation of AuNPs.