Inflammatory cytokines may hold the key to the clinical evolution of psoriasis. The aims of this study are to find a correlation between levels of inflammatory cytokines such as TNF-α, IL-23, IL-17A, and IL-17F and disease duration and severity scores in psoriasis; to test if the decrease in any of the aforementioned cytokines is correlated with an amelioration in disease severity scores; and to analyze if any of the four biologic agents used are linked with a greater decrease in overall cytokine levels. We enrolled 23 adult patients under treatment with ixekizumab, secukinumab, guselkumab, or adalimumab and measured psoriasis disease severity scores PASI (Psoriasis Area Severity Index) and DLQI (Dermatology Life Quality Index), as well as the levels of the aforementioned cytokines at the start of therapy and after 3 months of continuous treatment. Inclusion criteria were the presence of psoriasis, age above 18 years and the need to initiate biological therapy (lack of response to standard treatment). Biological therapies resulted in an amelioration of PASI and DLQI scores, as well as levels of TNF-α, IL-23 and IL-17F. Disease duration and PASI and DLQI scores did not correlate with cytokine levels except DLQI and IL-23 score, in a paradoxically inversely proportional manner. IL-23, in particular, could be a useful biomarker for checking treatment response in psoriasis.