Background: Thyroid hormones have a crucial role in the metabolism and proliferation of blood cells. Thyroid dysfunction causes different outcomes on blood cells such as anemia, erythrocytosis, leukopenia, thrombocytopenia, and in rare cases causes’ pancytopenia. It also alters RBC indices including MCV, MCH, MCHC, and RDW. Objectives: This is a cross-sectional descriptive study conducted in Almatama town during the period from September 2021 to January 2022, aimed to assess the effects of hypothyroidism and hyperthyroidism on blood cell count and RBC indices. Materials and Methods: Fifty patients with thyroid disease (24 hyperthyroidism, 26 hypothyroidism) and 20 healthy subjects served as controls. Whole venous blood samples were collected in EDTA anticoagulant container, mixed well, transferred to the laboratory according to standard procedures to avoid contamination, and then automatically counted for complete blood counts. Results: RBCs, HB, MCV, MCHC, and MCH, had statistically insignificant results in thyroid patients when compared with the control group (P. value 0.225,0.077,0.235,0.498,0.626) respectively. In hyperthyroid RBCs, HB, PCV, MCV, and MCH were statistically insignificant (P. value 0.388,0.951,0.123,0.575,0.148) respectively, and a statistically significant MCHC (P. value 0.0020). In hypothyroid HB, PCV, and MCH were, statistically significant (P. value 0.001,0.010,0.029) respectively, RBCs, MCV, and MCHC were, statistically insignificant (P. value 0.166,0.107,0.125) respectively. Conclusions: The hematological parameters were affected by thyroid disease, In case of patients with unknown hematological dysfunctions, must be evaluated for thyroid hormones. The follow-up of patients with thyroid disorders should have the complete blood count and patients diagnosed with anemia should be considered for thyroid conditions before iron treatment. Cases of anemia that resist therapy should be investigated for the case of thyroid dysfunction.