To investigate whether the expression of FK506 binding protein 51 (FKBP51) in the hippocampus, prefrontal cortex and hypothalamus regions is associated with susceptibility to chronic unpredictable mild stress (CUMS) in male rats and to elucidate the underlying mechanisms. Methods: Male SD rats were randomly subjected into control and CUMS groups. After four-week CUMS, rats exposed to CUMS were divided into susceptible and resistant groups based on the results of behavioral tests. Then, tissue samples were obtained from the hippocampus, prefrontal cortex, and hypothalamus to ascertain the expression of FKBP51 and glucocorticoid receptor (GR). Furthermore, the linear correlations between depressive behaviors and hippocampal FKBP51 expression in rats were analyzed. Subsequently, hippocampal neurogenesis was detected, and cytosolic and nuclear GR expression was observed in PC12 cells. Results: Compared with the control group, CUMS-susceptible rats exhibited elevated FKBP51 mRNA and protein levels and decreased GR mRNA and protein levels in the hippocampus, whereas there was no significant difference in the CUMS-resistant groups. The depressive behavior in rats was found to be positively correlated with expression of FKBP51 in the hippocampus. Additionally, elevated FKBP51 may affected neuron activity and the expression and intracellular distribution of GR. Conclusion: The elevated FKBP51 in the hippocampus may be involved in susceptibility to CUMS in male rats by affecting neuron activity and GR expression and its intracellular distribution.