Macrophage polarization affects tumor growth, metabolism, and many other tumor processes. M1 macrophages can promote antitumor immunity response. Signal transducer and activator of transcription 1 (STAT1) is one of the critical transcription factors in this process, which promotes the expression of a series of inflammatory molecules. STAT1 has been reported as a potential target of reactive oxygen species (ROS)-induced glutathionylation, while the glutathionylation of STAT1 in macrophages and its underlying regulatory mechanism remains unclear. Glutaredoxin 1 (Grx1) functions as a deglutathionylation enzyme, which regulates the activities of many proteins through reversing glutathionylation. GeneChip and RT-qPCR was first applied to test the mRNA level of Grx1 in M1 macrophages. Western blot was then used to evaluate the variations of the Grx1 protein expression in M1 macrophages. Next, immunoprecipitation was used to investigate the glutathionylated STAT1 in both wild-type and Grx1-/- mouse macrophages. Finally, the induced alterations of STAT1 activity and function by Grx1 in M1 macrophage were examined by western blot and RT-qPCR. In M1-type macrophages, the levels of Grx1 were elevated. Glutathionylation of STAT1 was negatively regulated by Grx1. Furthermore, depletion of Grx1 increased the activity of STAT1, and thereby promoted the mRNA level of C-X-C motif chemokine ligand 9 (CXCL9) during M1-type polarization of macrophages. Grx1 controlled deglutathionylation of STAT1, which in turn might regulate M1-type polarization of macrophages. © 2020 The Authors. Thoracic Cancer published by China Lung Oncology Group and John Wiley & Sons Australia, Ltd.