In implementations of a visitor engagement detection and control system for online sessions with a listing platform, a computing device implements a visitor engagement system to monitor user actions by the visitors with items listed by the listing platform, and map the user actions and the items listed by the listing platform to a timeline of the online session. An engagement module determines levels of visitor engagement in the online session based on the mapping of the user actions and the items, and initiates communication with a low-engagement visitor during the online session to increase an engagement level of the low-engagement visitor. In some cases, a communication is then established between the low-engagement visitor and a different low-engagement visitor, an engaged visitor, or an administrator of the listing platform.