Objective. In 2020, 5 million children died before reaching their 5th birthday, most of those deaths being preventable with the right resources and access to them. Investing in the health and wellbeing of the children of the world is an essential investment in the future and it is subsequently the main focus of numerous projects that have been implemented for decades by organizations globally. Material and methods. A secondary-type narrative review was carried out in compliance with the requirements for such research. The bibliographic sources were taken from the PubMed, Medline, WHO library and Information Center InfoMedica library databases. Criteria for selecting sources included: 1) key-words: Child Mortality in Southeast Asia; Under-Five Mortality Rate; Millennium Development Goal; United Nations Children’s Fund, United Nations; 2) sources published until 31 January, 2022. Results. There was a significant decline of 76% in under-five mortality rate in Southeast Asia, in the last three decades. From 2000 to 2009, the mortality rate has decreased annually by 6.0%. In the last decade this number has decreased to an annual rate of reduction of 4.7%. A significant decline of over 50% has been obtained from 2000 until 2020, and a continuous, yet less rapid decrease in child mortality has been maintained. The target for 2030 set by the United Nations Sustainable Development Goals is for all regions to reach a rate of 25 deaths per 1000 live births. In 2020, according to data collected by the United Nations Children Fund and United Nations Inter-Agency Group for Child Mortality Estimation the Eastern and Southeast Asian regions had a child mortality rate of 14 deaths per 1000 live births, hence already reaching the target goal. Although the under-five mortality rate in Eastern and Southeast Asia has decreased considerably in the last 20 years and has reached in 2020 the Sustainable Development Goals country target goal, it is important to keep in mind that the data is averaged amongst all the countries that this region is comprised of. Thus, although the regional data looks promising, a noticeable gap can be noticed between the individual countries located in this region. The reduction in under-five mortality rates is unevenly distributed among and within the countries in the Southeast Asian region. In 2011, of the ten countries in the Association of Southeast Asian Nations, only Brunei, Singapore, and Malaysia had infant and child mortality rates below 10 per 1000 live births. Infant and under-5 mortality in Thailand and Vietnam have substantially declined to below 15 per 1000 live births, but the Philippines and Indonesia have seen a levelling off in rates to between 30 and 50 per 1000 live births. Myanmar, Cambodia, and Lao PDR still have mortality levels of 50-70 per 1000 live births in 2008, which are similar to the rates of their neighbors from more than two decades ago, and ranked among the highest for Asia. Conclusion. A significant decline of 76% has been achieved in under-five mortality rate in Southeast Asia, in the years 2000-2020. Southeast Asia has reached in 2020 the Sustainable Development Goals 3.2 target, although a significant gap is present in the mortality rates of individual countries located in this region. The programmers with the most success in decreasing child mortality rates in Southeast Asia have been Millennium Development Goals and Sustainable Development Goals, implemented in 2000 and 2015, respectively. Furthermore, 11 million under-5 deaths could be prevented globally between 2020 and 2030, if all the countries work towards meeting the Sustainable Development Goals target on under-5 mortality. To further the progress in reducing the under-five mortality rate in underdeveloped countries in Southeast Asia, cooperation at all levels of society, ranging from families and communities to health care workers and governments is required.