HIV-associated/epidemic Kaposi's sarcoma (EpKS) is an AIDS-defining angio-proliferative malignancy. It can be treated with antiretroviral therapy (ART) alone or with ART plus cytotoxic chemotherapy. ART-treated EpKS can either respond or worsen upon treatment. This study aimed at identifying immunological markers of ART-treatment response. We compared responders (those with clinical EpKS tumor regression) versus poor responders (those with progressive or non-responsive EpKS). We measured plasma cytokine and chemokine levels using cytometric bead assays. Kaposi's sarcoma herpesvirus (KSHV) neutralizing antibody (nAb) responses were also quantified to test associations with treatment outcome. Interleukin (IL)-5 levels were significantly elevated in responders versus poor-responders at baseline (0.76pg/ml vs. 0.37pg/ml; p<0.01) and follow-up (0.56pg/ml vs. 0.37pg/ml; p<0.01); IL-6 was lower in responders than poor-responders at follow-up (600fg/ml vs. 4272fg/ml; p<0.05). IP-10/CxCL-10 was significantly lower at follow-up in responders versus poor-responders (187pg/ml vs. 528pg/ml; p<0.01). KSHV nAb were not significantly differential between responders and poor-responders. In conclusion, high plasma IL-5 at baseline could be a marker for ART-treated KS tumor regression, whereas increased pro-inflammatory cytokine IL-6, and the chemokine IP-10, associate with KS tumor progression.