Background Southeast Asian ovalocytosis (SAO) is a red blood cell membrane disorder caused by a 27 base pair (bp) deletion in the SLC4A1 that transcribes to a truncated variant of band-3 glycoprotein. β-Thalassemia is another red blood cell disorder, caused by mutant alleles in the β-globin gene that lead to globin chain impairment. Both conditions occur in Southeast Asian countries, including Malaysia. Objectives This report describes hematological and molecular features of a patient with both SAO and β-thalassemia and her children. Methods A 58-year-old Malay woman presented to our clinic with dizziness, tiredness, and easy fatigability. She was mildly anaemic. Analysis of her complete blood counts and her peripheral blood smear revealed microcytic hypochromic anaemia with large numbers of macro-ovalocytes and stomatocytes. Results Hemoglobin and globin gene studies revealed heterozygous β-thalassemia, and further analysis demonstrated a heterozygous 27 bp deletion on the SLC4A1 gene consistent with SAO. Analysis of the patient’s offspring showed co-inheritance of β-thalassemia and SAO in her elder daughter and son, and SAO alone in another daughter. Conclusions High frequencies of SAO and different β-thalassemia mutations are present in the Malaysian population, thus coinheritance of SAO and β-thalassemia is not uncommon. However, this coinheritance is rarely reported, possibly because the red blood cell indices are overlooked and peripheral smear examinations are not routine.