Understanding the past human adaptations to the environmental changes along the southern coastal area of Sri Lanka caused by sea-level fluctuations during the Holocene period has not yet been clearly understood. The present study aims to interpret the interactions between humans and the environment during the Holocene. Sequential soil samples were obtained from test pits and exposed profiles at five selected prehistoric human occupation sites located in the southern coastal area. The stratigraphy, which was determined based on field investigations and, the grain size distribution and textural parameters of soil samples were employed to establish the depositional environments of the study sites. The stratigraphy and, textural characteristics of sediments at Pallemalala, Mini-Athiliya and Kalametiya revealed that marginal lagoonal and fluvial environmental conditions have prevailed as a result of Mid-Holocene sea-level fluctuations. Conversely, the stratigraphy and sediments at Bundala indicate the influence of storm waves. In addition, Henagahapugala assumed to be occupied by prehistoric populations, seems to be a river channel and reveals comparatively less evidence of human occupation. This evidence indicates that the marginal fluvial/ marine environments were preferred by prehistoric people due to the accessibility and availability of a variety of highly nutritious dietary resources, freshwater sources and source materials for stone implements. Therefore, it is possible to conclude that the marginal environments created by Mid-Holocene sea-level fluctuations resulted in technological and cultural transformations of prehistoric people in Sri Lanka.