Several studies have outlined a possible relationship between an increased body mass index (BMI) and respiratory allergic diseases, such as asthma and rhinitis. Very recently, it has been demonstrated that serum adipokines, such as leptin and adiponectin, may be increased in patients with allergic rhinitis. The aim of the study was to evaluate the serum leptin and adiponectin levels in a cohort of patients with pollen-induced allergic rhinitis, before and after a single preseasonal course of sublingual immunotherapy (SLIT). A total of 41 patients (22 male and 19 female, median age 39 years) with AR due to pollen allergy, along with 34 normal subjects, were included in the study. Blood sampling for assessing serum adipokines, immunoglobulin E (IgE) levels, and eosinophils were performed in all subjects before and after the SLIT course. An increasing trend of both adipokines was observed after SLIT, albeit without statistical significance and with gender difference. Leptin was significantly related to some clinical parameters and peripheral eosinophil counts. Conversely, adinopectin showed an inverse significant correlation with peripheral eosinophils counts but only for men. In conclusion, the results of this preliminary study show that a single preseasonal SLIT course does not induce significant modifications in serum adipokines levels but induces only a slight increase.