Diverse causes of accidents abound on construction sites, which lead to complexity and difficulty in understanding the key causes of accidents on construction sites. The effect is the increasing rate of accidents. Thus, grouping and identifying the key dimensional and sub causes of accidents is important. However, there is a dearth of research on the dimensionality and indicators of causal factors of accidents on construction sites. This paper aims to create an avenue for easy identification and understanding of the causes of accidents through the development of key indicators and dimensional causes of accidents on construction sites. Adopting a cross-sectional survey research design, three hundred questionnaires were purposely distributed to construction workers who have had experience or witness accidents on a construction sites. Two hundred questionnaires were retrieved and used for analysis representing a 67% response rate. An exploratory factor analysis was used to group and find the significant causal factors from the 64 factors identified in the literature. From the analysis, five key dimensional causes with 22 indicators were identified namely; personal and work factors, design factors, behavioural factors, proximate factors and attitudinal factors. The key indicators identified among others are non-use of PPE, lack of experience, working in confined spaces, disobedience to work discipline and innovative technology. To reduce the occurrence level of accidents, site managers should place the key indicators and dimensional causal factors of accidents on the signboard for easy identification and understanding and as a training guide on construction sites.