Patients with heterozygous β-thalassemia are generally asymptomatic. However, the intermediate phenotype is uncommon, and patients require further investigation to confirm the diagnosis. We describe a 32-year-old woman (gravida 3, para 2) with heterozygous β-thalassemia who presented with symptomatic anemia and had a history of frequent blood transfusion in each pregnancy. Physical examination was unremarkable. Laboratory results at presentation showed hypochromic microcytic anemia with reticulocytosis. Molecular study revealed intermedia phenotypes resulting from coinheritance of heterozygous β-globin chain mutation (IVS1-5) and a rare heterozygous α-globin triplication (αααanti-3.7). In this case report, we discuss the laboratory diagnostic approaches and the challenges faced in investigating this case.