The tuning of parameters of controller is crucial while designing a controller for a system. In this brief, a new meta-heuristic optimization, i.e., gray wolf optimization (GWO), is utilized for tuning of proportional–integral (PI) controller for two-tank system. The integral of squared error (ISE) is minimized for deriving controller’s parameters. ISE is formulated in terms of alpha and beta parameters. Thus, the formulated ISE is minimized using GWO and other state-of-the-art algorithms. A comparative study is also performed in which time-domain specifications and responses of system are compared. Detailed study proves that GWO provides better results when compared to other algorithms. © Springer Nature Singapore Pte Ltd. 2019.