Abstract: A safety rail mounting bracket system comprising a first rail holder having a first base plate carrying an upper mounting bracket and a lower mounting bracket for releasably carrying rail members. A second rail holder having a second base plate carrying an upper mounting bracket and a lower mounting bracket for releasably carrying rail members. The first base plate is mounted to a first wall defining a first side of an opening and the second base plate is mounted to a second wall opposite the first wall and defining a second side of the opening. The mounting brackets on the first and second base plates are space apart a predetermined distance to comply with applicable regulatory requirements so that the rail members are properly positioned within the opening.