Due to socio-demographic and technological changes, companies face new challenges to achieve an efficient and competitive production. Increasing cost and time pressure combined with an aging workforce with declining physical and mental performance requirements, as well as the increasing shortage of skilled workers, lead to reduced productivity. Therefore, the reduction of human-caused errors is becoming more important. This paper analyzes the connection between human-caused work errors, mental and physical strain, and workplace ergonomics. Four variables are used to analyze the interaction between ergonomics and work errors within the framework of a study in manual assembly. The study sample consists of 21 employees from a manual truck assembly at six different workstations. Models with different combinations of variables are developed in a multiple linear regression framework. Regression model (RM) 1 predicts the variance of the criterion work error with the predictors NASA-RTLX, Borg, and EAWS. It has high predictive power (adjusted R² = 0.746) but is not significant.