Background/Objectives: Obesity is a public health problem with hematological consequences in developing nations. This study aims to evaluate the impacts of obesity on hematological parameters such as: Neutrophil-Lymphocyte Ratio (NLR) and monocyte count among adults in Sapele. Materials and Methods: This cross sectional and descriptive study was carried out at Central Hospital, Sapele, General Hospital, Oghara and Biomed Diagnostic Centre, Sapel all in Southern Nigeria. 415 subjects with age between 18 and 65years were enrolled for this study including 312 obese experimental subjects (comprising of 111males and 201females) and 103 non-obese normal control subjects (comprising 40males and 63females). 5.0mls of venous blood was collected from all subjects into EDTA container and Full Blood Count (FBC) was determined using Sysmex XN330 automated hematology analyzer while NLR was calculated from the FBC results. Collated data were analyzed using Student’s t-test, One-way ANOVA, LSD post-hoc test and results were expressed as mean ± standard deviation. Results: Body-Mass-Index (BMI) of obese and control subjects were 36.82±0.55kg/m2, and 20.43±0.29 kg/m2, respectively at p<0.001. Obese subject had hemoglobin (HB) concentration of 125.39±1.26g/dl, the HB of control group was 127.27±1.75 g/dl at p>0.05. On the other hand, Monocyte count for Obese subject was 6.40±0.23 X 109/l, while control group had monocyte count of 5.14±0.18 X 109/l, at p<0.001. Furthermore, the Neutrophil Lymphocyte Ratio (NLR) of obese and control subjects was 1.57±0.21 and 1.18±0.05 respectively. Conclusion: Obese subjects had significantly higher values of BMI, NLR, Monocyte count at p<0.05 when compared with control subjects in Sapele, Southern Nigeria.