A transmission system that manages sessions established among a plurality of transmission terminals. The transmission system includes a terminal information request signal transmission part that transmits, from a first transmission terminal, a terminal information request signal to request information for identifying a third transmission terminal currently establishing a session with a second transmission terminal that is designated by a user as a destination; and a display part that carries out display in such a manner that the user can determine whether to allow the third transmission terminal to establish a session with the first transmission based on information received in response to the terminal information request signal. The information includes first information for identifying a transmission terminal eligible to establish a session with the first transmission terminal and second information that is the information for identifying the third transmission terminal currently establishing the session with the second transmission terminal.