Aim: The aim of this study is to investigate some immuno-haematological characteristics of Nigerian sickle cell disease (SCD) patients in asymptomatic steady state. Material and Methods: Thirty asymptomatic SCD patients and 30 apparently healthy age- and sex-matched non-sickle cell disease individuals were investigated. The packed cell volume, white blood cells and differentials, and platelet counts were done on automated blood cells counter, while the ESR was determined by Westergren’s technique. C3 activator, C1-INH, IgA, IgG and IgM were estimated by the single radial immuno-diffusion method. Results: The SCD patients had elevated ESR and a significantly higher total leukocyte count compared to the controls (t= 5.22, p= 0.000). A positive correlation was found between ESR and C3 activator (r= +0.449, p= 0.047), and between ESR and serum IgM levels (r= +0.531, p= 0.016). Serum levels of IgA and C3 activator were significantly higher in SCD subjects (IgA: t= 2.47, p= 0.019; C3 activator: t= 2.79, p= 0.009), while the levels of C1-INH and IgM, though higher in SCD subjects, were not significant. Conclusions: It could be concluded from this study that immune dysfunction are evident in Nigerian SCD patients.