Populasi di negeri Sabah telah mengalami peningkatan sejak pascamerdeka sehingga tahun 2000-an. Situasi ini mendapat perhatiandaripada pelbagai pihak sehingga timbul desakan untuk membuatsiasatan terhadap permasalahan tersebut. Kesannya, Royal Commision ofInquiry (RCI) dibentuk bagi menyiasat sebab berlakunya pertambahanmendadak penduduk di Sabah. Justeru kertas kerja ini akan menganalisisaspek demografi dan non-demografi bagi mengenal pasti sebabberlakunya pertambahan populasi penduduk selain kesan setelahberlakunya lebihan populasi di Sabah. Kajian ini menggunakanpendekatan kualitatif dengan menggunakan pendekatan disiplin ilmu-ilmusains sosial lain seperti sosiologi, antropologi, sains politik danekonomi digunakan sebagai ilmu bantu. Berdasarkan analisis yangdigunakan, kajian ini mendapati berlaku lebihan populasi pendudukyang ketara di Sabah sekitar 1970-an akibat daripada faktor migrasipenduduk. Lebihan populasi yang berlaku menyebabkan pelbagai kesansosial seperti kemiskinan dan jenayah yang meningkat di Sabah. The population in Sabah has increased since post-independence until the2000s. The situation is getting attention from various parties so it is urgedto investigate the problem. As a result, the Royal Commission of Inquiry(RCI) was formed to investigate the reason for the sudden increase inpopulation in Sabah. Hence, this paper will analyze the demographic andnon-demographic aspects to identify the reason for the increase inpopulation populations apart from the effects of excessive populations inSabah. This study uses qualitative approaches by using disciplinesapproaches to other social sciences such as sociology, anthropology,political science and economics as auxiliary sciences. Based on the analysisused, this study found that there was a significant population surplus inSabah around the 1970s as a result of population migration factors.Population surplus prevails causes various social impacts such as povertyand rising crime in Sabah.