Interleukin-10 (IL-10) is a key immunoregulatory cytokine implicated in asthma pathogenesis. This case-control study investigated the association of three IL-10 promoter polymorphisms (−1082 G > A, −819 C > T, and −592 C > A) with asthma susceptibility and immune cell profiles in a Mauritanian pediatric population. Fifty-four asthmatic children and 45 controls were genotyped by PCR-RFLP and Sanger sequencing. Allele/genotype frequencies were compared by chi-square test, haplotypes by Haploview, and IgE, leukocyte, and platelet counts were analyzed using non-parametric tests. The −592 C > A polymorphism was significantly associated with asthma, with the A allele more frequent in cases and the CA genotype increasing risk. The −1082 G > A polymorphism showed a significant genotype association, with the GA genotype protective and the AA genotype observed only in cases. The ACG haplotype showed a trend toward increased risk. Asthmatic children exhibited higher IgE levels, neutrophil and basophil percentages, and lower lymphocyte, monocyte, and platelet counts. The −1082 G > A variant was associated with neutrophils and monocytes in the overall population. Stratified analysis revealed disease-specific effects: −819 C > T influenced monocytes in cases, while −592 C > A affected eosinophils in controls. IL-10 promoter polymorphisms, particularly −592 C > A, are significantly associated with pediatric asthma susceptibility, with −1082 G > A showing an additional protective effect. Asthmatic children display a mixed inflammatory profile of elevated neutrophils and basophils alongside reduced lymphocytes and monocytes. The −1082 G > A, −819 C > T, and −592 C > A variants show immunomodulatory effects on leukocyte composition in a disease-context-dependent manner. Replication in larger cohorts with functional IL-10 measurements is warranted.