Gap junctions (GJ) are transmembrane channels that connect the cytoplasms of adjacent cells, thereby facilitating the rapid exchange of ions, second messengers, and metabolites smaller than 1 kDa. Connexin 43, the best-studied GJ protein, is a component of the Sertoli cell barrier/blood–testis barrier (BTB). To gain insight into the biology of the BTB, we investigated the effects of interleukin 1alpha (IL1A), a pro-inflammatory cytokine that disrupts BTB function, on gap junctional communication (GJC) in Sertoli cells. Compared with controls, the levels of connexin 43 and connexin 43 (Ser 368) increased ~ 30- and 20-fold, respectively, at 24 h after IL1A treatment. To assess GJ function, we investigated fluorescence recovery in photobleached Sertoli cells after vehicle or IL1A treatment. Compared with the control, IL1A affected the ability of calcein to return to photobleached cells, indicating that GJC was compromised. To explain the effects of IL1A on GJ function, the involvement of the Sertoli cell cytoskeleton was investigated. Stress fibers aggregated at the periphery of Sertoli cells treated with IL1A. These results were substantiated by a biochemical assay that showed IL1A to disrupt the bundling of exogenous F-actin by Sertoli cells. In summary, IL1A regulates GJC in Sertoli cells, which is critical for BTB restructuring.