Manual activities of workers in palm oil factories cause pain complaints that can be resolved with an ergonomic program. However, the uncertainty of the success of the ergonomic program requires active involvement from workers. This study aims to discuss the role of workers’ perceptions towards the success of the ergonomic program intervention in palm oil mills. By referring to the theory of reasoned action and technology acceptance model, acceptance of workers to ergonomics programs are influenced by perceived usefulness, perceived ease of use, and perceived trust. All these research variables were analyzed simultaneously using Partial Least Squares Structural Equation Modeling (PLS-SEM) software, in which data were obtained from questionnaires given to 280 people working in 20 palm oil mills in North Sumatra Province. The sampling method used is simple random sampling and model estimation is performed using PLS regression algorithm and resampling bootstrapping method. The result shows that perceived usefulness has the biggest effect on the success of the ergonomic program, followed by perceived trust and perceived ease of use, which has a smaller effect. This study focuses on workers’ perception that needs to be considered for facing uncertain results in implementing an ergonomic program.