This article addresses the fault estimation and nonfragile synchronization control for multiweighted complex dynamical networks against deception attacks. An event‐triggered mechanism is proposed to reduce the redundant data transmission over the communication networks. Considering the network communication security, this article investigates deception attacks in the observer, where the adversary attempts to inject some false data in the measurement output to modify the transmitted signal in the communication networks. Some stochastic variables obeying the Bernoulli distribution are expressed to describe the probability of the deception attacks, which is determined by an attacker. Then based on Lyapunov stability theory, robust analysis method, some novel solvability criteria are presented such that the resultant augmented error system is asymptotically stable with a guaranteed H∞$$ {H}_{\infty } $$ performance index. Further, the existence criterion of the desired event‐triggered estimator is proposed in terms of a set of linear matrix inequalities. Finally, two illustrative examples including an F‐404 aircraft engine model are provided to verify the effectiveness of the developed estimator design method.