The accuracy required in small-field dosimetry for stereotactic radiosurgery imposes limitations on the conventional dosimetric calibration protocols used in radiotherapy. This study presents the development and validation of a computational model of the CyberKnife® system using the Monte Carlo method with the MCNP6 code. The main objective is to establish a validated computational model that enables future research and clinical applications in stereotactic radiosurgery. The model was developed to validate the 60 mm conical collimator, and the results were compared with experimental data from percentage depth dose (PDD) and lateral dose profile (LDP) curves at depths of 10 cm and 20 cm. The analyses revealed the influence of field size and photon source characteristics on the dose distribution, showing good agreement between the simulated and measured data within the established tolerance limits. These findings demonstrate that the proposed model accurately reproduces the CyberKnife® beam behavior and serves as a robust and promising tool for the investigation of treatment variables, support of therapeutic planning, and optimization of stereotactic radiosurgery protocols.