Dengue is an important infectious disease that has high morbidity and mortality rates in most tropical and subtropical areas of the world. The diversity of the clinical manifestations involved in the outcome of dengue virus infection is affected by the relationship between serotype/genotype of the virus, host immune status, host genetic background, and environmental factors. Polymorphisms in interleukin (IL) genes have been associated with risk of developing symptomatic dengue. This study aimed to determine the association of the single-nucleotide polymorphisms of IL1β -511C>T, IL1RN 86 bp VNTR, and IL6 -174G>C genes with the clinical features of 198 individuals admitted to the São José Infectious Diseases Hospital with suspected dengue infection. Dengue was confirmed in 118 of the patients. The control group consisted of 80 other individuals who had symptoms similar to dengue, but negative for that. A higher frequency of increased hematocrit (p = 0.009), leukopenia (p = 0.000007), neutropenia (p = 0.0004), lymphocytosis (p = 0.00001), monocytosis (p = 0.004), atypical lymphocytes (p = 0.03), and thrombocytopenia (p = 0.0000009) was observed in the dengue patients. Among the polymorphisms studied, only IL1β (-511C>T) was associated with dizziness, (p = 0.01), suggesting that IL1β may be related to hypotensive episodes and increased vascular permeability. These results pointed out the importance of the IL1β (-511C>T) polymorphism in the development of clinical symptoms of dengue symptomology.