Sphingolipids (SLs), are structural components of the skin that contribute to the regulation of the proliferation and differentiation of keratinocytes as well as regulation of the skin epidermal barrier. A prospective cross sectional comparative controlled study was designed to evaluate the serum level of sphingosine 1 phosphate (S1P) and ceramide (CER) before and after narrow band ultraviolet B (NBUVB) in psoriatic patients. The study included 32 patients presented with psoriasis and 32 healthy age and sex matched control volunteers. (S1P and CER) levels were measured before and after NBUVB sessions for psoriatic patients and their levels were correlated to psoriasis area and severity index (PASI) improvements. PASI scores and serum values of the studied sphingolipids demonstrated a significant difference between the baseline and at the end of the 12 weeks NBUVB treatment. A statistically significant positive correlation was established between psoriasis severity and S1P serum levels before and after treatment while no correlation was observed between psoriasis severity and CER serum levels. Decreased total CER and increased S1P serum levels reflect altered sphingolipid metabolism in psoriasis and can be predictors of disease severity.