Breast cancer is the most common female malignancy both in Nigeria and globally. The aim of this case-control study was to determine the changes in some haematological parameters among breast cancer patients in Sokoto, Nigeria. The study included a total of 46 breast cancer subjects (mean age 42.91 ± 5.83 years) visiting the Specialist Hospital, in Sokoto, North Western Nigeria. A total of 46 apparently healthy age-matched women were monitored as control. Some haematological (packed cell volume, total white blood cell count and platelet count) were analyzed using the auto-haematology analyzer (Genesis, HA6000). Breast cancer staging was determined using the TNM classification. Data were analyzed using SPSS 22.0 statistical package. A p-value ≤0.05 was considered significant in all comparisons. The result indicated that patients with breast cancer had a lower mean packed cell volume (29.20 ± 0.50 %) compared to controls (36.20 ± 0.42 %) (p=0.000). The mean total white blood cell count of patients was also statistically lower among breast cancer patients (3.91 ± 0.19×10 9 /l) compared to controls (4.38 ± 0.13×10 9 /l) (p=0.045). There were no statistically significant differences in the mean value of platelet counts of breast cancer patients (197 ± 5.06×10 9 /l) and controls (207 ± 5.84×10 9 /l) (p=0.217). Newly diagnosed patients who were not on therapy had significantly lower mean values of PCV compared to controls (p<0.05). There were no statistically significant differences in the mean values of total white blood cell counts and platelets count of newly diagnosed patients that are not on therapy and controls (p>0.05). The mean PCV levels were significant lower as compared to controls (p<0.05) Patients that were on chemotherapy had significantly lower values of PCV, total white cell counts and platelets compared to patients who were not yet on any therapy (p <0.05). There were no statistically significant differences in the PCV, total white blood cell counts and platelets based on the different stages of breast cancer (p >0.05). Findings of this study have shown that breast cancer patients had a lower PCV and TWBC count compared to controls. Chemotherapy further exerts adverse effects on patients as seen with the significantly decreased values of haematological parameters on patients on therapy. Findings of this study also shows that breast cancer patients have low PCV and WBC count compared to controls. Haematological investigation should be taken as an essential tool in the investigation and management of breast cancer. Active breast cancer awareness campaign should be carried out on the need for early diagnosis. More research should be carried out to investigate the pattern of other haematological parameters in breast cancer disease.