This study is aimed at characterizing a single Cobalt-60 source capsule of the Gamma Knife Perfexion™ unit using the BEAMnrc Monte Carlo code. The Gamma Knife Perfexion™ source capsule was modeled using the BEAMnrc user code according to the manufacturer's technical details. The modeled parts include the source, the area around the source, and the capsule. The cylindrical source is 1mm in diameter and 17mm in length, with a physical density (ρ) of 8.9 × 103kg/m3. The simulation parameters were an electron cutoff energy (ECUT) of 0.7meV and photon cutoff energy (PCUT) of 0.01meV. Energy fluence was calculated on a 0.25cm diameter scoring plane located 3.1cm from the source. Simulations were performed with and without the encapsulation of the source to investigate its effect on the spectrum and fluence of emitted gamma rays. The results showed that the influence of source encapsulation on the gamma rays is an increase in the relative number of particles in each energy bin of aggregate gamma rays by 92.36% at 0.23meV energy and 66.12% at 1.10meV energy. The secondary gamma rays were found to increase by 94.17% at 0.23meV energy and 63.74% at 1.10meV energy. The encapsulation of the source attenuated the gamma rays, which altered the spectrum. The mean energy of the beam increased, thereby exhibiting a beam-hardening effect.