Extinguishing the previously acquired fear is critical for organism’s adaptation to the ever-changing environment, a process requiring the engagement of GABAA receptors (GABAARs). GABAARs consist of tens of structurally, pharmacologically and functionally heterogeneous subtypes. However, the specific roles of these subtypes in fear extinction remain largely unexplored. Here, we observed that in the medial prefrontal cortex (mPFC), a core region for mood regulation, the extrasynaptically-situated, δ subunit-containing GABAARs (GABAA(δ)Rs), had a permissive role in tuning fear extinction in male mice, an effect sharply contrasting to the established but suppressive role by the whole GABAAR family. First, the fear extinction in individual mice was positively correlated with the level of GABAA(δ)R expression and function in their mPFC. Second, knockdown of GABAA(δ)R in mPFC, specifically in its infralimbic subregion (IL), sufficed to impair the fear extinction in mice. Third, GABAA(δ)R-deficient mice also show...