A proportional-integral controller retuning is performed on formaldehyde production process at PT X. Retuning is carried out to improve the controller performance on the process. The process model is estimated by a first order plus dead time model (FOPDT), and then the controller parameters are tuned using the Ziegler-Nichols (PRC), Wahid-Rudi-Victor (WRV), Cohen-Coon, autotuning, and fine tuning. The controller performance is tested using set point (SP) tracking and disturbance rejection with integral of square error (ISE) as performance indicator. There are three controllers that are tested, i.e., the steam flow controller (FIC-102), air temperature controller (TIC-101), and tank level controller (LIC-102). Fine tuning method provides a better control performance for FIC-102 and TIC-101, while autotuning method provides a better control performance for LIC-102 compared to the previous settings in the field. Performance improvement for set point (SP) tracking are 81,59% (FIC-102), 94,11% (TIC-101), and 85,61% (LIC-102). While performance improvement for the disturbance rejection are 95,5% (FIC-102), 94,53% (TIC-101), 93,16% (LIC-102). Thus, retuning PI controllers work well and by using the suggested controller tuning, a better controller performance of PT X can be achieved. © 2020 Author(s).