This article is concerned with the event-triggered guaranteed cost control for a class of Markovian jump systems with time-varying delays and partly unknown transition probabilities, which is described by the Takagi-Sugeno fuzzy model. For the sake of saving network bandwidth, an event-triggered mechanism related to system modes is developed in the feedback channel, in which network-induced delay randomly occurs. The stability criterion for the system with a guaranteed cost index is derived by the Lyapunov-Krasovskii functional. Moreover, sufficient conditions that ensure the existence of the admissible fuzzy controllers are given. By means of the proposed approach, the fuzzy control gains and event-triggered parameters can be codesigned. Finally, some simulation results are presented to demonstrate the superiority and effectiveness of the developed method.