Post-traumatic stress disorder (PTSD) is a neuropsychiatric disorder characterized by changes in behavior and personality. Long Interspersed Nuclear Element 1 (LINE-1) is a retrotransposable element expressed in early development that is later repressed. Adult expression of LINE-1 is active under pathological conditions, and evidence in humans show a correlation between PTSD patients and LINE-1 expression. Here we aimed to understand if LINE-1 expression influences the development of PTSD in mice. Single Prolonged Stress (SPS) was used to induce PTSD in P60 mice. PTSD development was determined by behavioral testing. Changes in LINE-1 expression were determined by RT-qPCR in hippocampus and cortex. Methylation of the DNA promoter sequence of LINE-1were performed by bisulfite sequencing. Induction of PTSD by SPS shows that 79% of animals developed PTSD and 21% were resistant. RT-qPCR analysis showed a differential increase in LINE-1 expression between hippocampus and cortex in resistant animals compared to control and susceptible, while bisulfite sequencing of LINE-1 promoter revealed changes on CpG and non-CpG methylation among the groups. Our findings suggest that LINE-1 expression influences the development of PTSD, opening the possibility to use it as therapeutic target to prevent or treat this neuropsychiatric disorder.