Acute graft-versus-host disease (aGVHD) is a serious complication after stem cell transplantation and is associated with high non-relapse mortality. If steroid treatment as first-line therapeutic approach fails, treatment options are limited. In retrospective studies, ruxolitinib, a selective Janus kinase 1/2 inhibitor as well as extracorporeal photopheresis (ECP) could show high efficacy in treatment of steroid refractory acute and chronic GVHD. Here, we report single-center experience of combining JAK-inhibitor treatment with ECP in 18 patients with severe steroid refractory aGVHD of lower GI-tract. The treatment was well tolerated and no severe cytopenia (grade IV) occurred, in three patients grade III cytopenia could be observed. Response was complete or partial in 44% and 11%, respectively, resulting in an estimated 2 year overall survival of 56%. Steroids were tapered rapidly with a median time of 2 days for halving of dosage avoiding additional steroid-associated side effects. Under treatment with ruxolitinib and ECP, an increased level of regulatory T cells could be observed elucidating direct effects of this treatment on immune response.