Introduction: Thalassaemia is an autosomal recessive disorder affecting 5 percent of the Malaysian population. The state of Sabah has the highest number of transfusion dependent thalassaemia and β-thalassaemia carrier in Malay-sia. For Malaysia to be successful in the prevention of thalassaemia, Sabah needs to be focused on the preventive activities in areas with high prevalence of β-thalassaemia carriers. Thus, identifying the mapping of β-thalassaemia is crucial for planning for prevention activities. The objective of this study was to identify the prevalence of β-thalas-saemia by districts and ethnic groups in Sabah. Methods: This study used data from Form 4 Thalassaemia Screening Records in 2017. The data were cleaned and analysed using Excel spreadsheet to calculate for the national and state specific prevalence of β-thalassaemia carrier. Subsequently, the data was used for mapping of high-risk districts and ethnic groups in Sabah. Results: A total of 31,655 Form 4 students from 242 secondary schools were screened in Sa-bah in 2017 and 1150 (3.6%) were diagnosed as β-thalassemia carrier. The prevalence of β thalassaemia carrier was higher in the West Coast of Sabah which include Kota Marudi District (11.1%), Nabawan (9.0%), Tambunan (8%), Tongod (7.5%), Ranau (7.0%), Kota Belud (5.0%), Kudat (4.6%), Tenom (4.1%) and Tuaran (4.0%). In the East Coast of Sabah, there was only the Beluran District (5.0%) had prevalence that higher than the state average. β-thalassae-mia carriers were more likely to be of Dusun, Kadazan Dusun followed by Bajau, Murut and Rungus ethnic group. Conclusion: The distribution of β-thalassaemia carrier in Sabah was concentrated in the West Coast of Sabah and more common among the Dusun, Kadazan Dusun followed by Bajau, Murut and Rungus ethnic group. Thus, the thalassaemia prevention activities should be focuses in these areas and ethnic groups.