Drowning or asphyxiation is one of the top five types of construction accidents on-site in the world. Few studies focus on the causes and sub-factors that contribute to drowning/asphyxiation in Malaysia's construction industry. This paper developed an Analytic Hierarchy Process (AHP) model for the factors and sub-factors for drowning/asphyxiation and determined their relative weights and priorities. Worker's unsafe actions have a maximum weight of about 80.98 for the significant factors based on the proposed AHP model, followed by hazardous site conditions with 10.89 and management factors with 8.13. Financial constraint carries the most weight with 20.22 for the management factors, unsafe working and operating procedures in a confined space, and water bodies have the most weight with 26.97 for hazardous site conditions. Rushing to complete the job and failure to comply with standards working procedure in a confined space or water bodies have the most weight with 17.24 each. This study can help safety practitioners understand the primary factors and sub-factors responsible for drowning and asphyxiation, how they can reduce the risk of fatal accidents on-site, and how they can make prompt safety decisions. The proposed model also provides a tool to determine the appropriate and effective drowning/asphyxiation prevention methods. © Published under licence by IOP Publishing Ltd.