Workers’ compensation insurance is imperative for construction projects to safeguard the interests of workers and contractors. The commitment of insurers under this insurance is extremely broad. They must therefore accomplish rigorous risk and market assessments to decide optimal premiums. General insurers in Singapore have been experiencing detrimental loss-ratios in this business due to the lack of a proper framework that encompasses all the critical variables. The purpose of this study is to identify and explore the critical variables for premium-rating of construction workers’ compensation insurance. An extensive literature review helped identify 17 variables that may influence premium rates. An interview questionnaire survey and subsequently a statistical analysis of the survey data were carried out to identify the critical variables. Eight variables were found significant for insurers for premium-rating including: wage roll, project hazards, project safety, contractor’s claims history, insurer’s overhead costs, insurer’s corporate objectives, competition, and investment income from underwritten premiums. The findings of this study can be used by insurance companies in their risk assessment and premium-rating exercises.