Purpose: To evaluate the effectiveness of an individually tailored intervention for improvement in lifestyle behavior, health indicators, and prevention and reduction of overweight among construction workers. Design: Randomized controlled trial. Setting: Various blue-collar departments of a large construction company in the Netherlands. Participants: Blue-collar workers randomized to an intervention (n = 162) or a control group (n = 152). Intervention: The intervention group received individual coaching sessions, tailored information, and materials to improve lifestyle behavior during a 6-month period, and the control group received usual care. Measures: Body weight, body mass index (BMI), waist circumference, physical activity (PA) levels, dietary behavior, blood pressure, and blood cholesterol were assessed. Analysis: Effectiveness of the intervention on outcome measures at 6- and 12-month follow-up was assessed by using linear and logistic regression models adjusting for baseline levels. Results: After 6 months, a statistically significant intervention effect was found on body weight ( B = −1.06, P = .010), BMI ( B = −0.32, P = .010), and waist circumference ( B = −1.38, P = .032). At 6 months, the percentage of those meeting public health guidelines for PA increased significantly in the intervention group compared to the control group ( B = 2.06, P = .032), and for sugar-sweetened beverages, an intervention effect was found at 6 months as well ( B = −2.82, P = .003). At 12 months, for weight-related outcomes, these differences were slightly smaller and no longer statistically significant. The intervention was not effective on the total amount of moderate to vigorous PA and other dietary and health outcomes. Conclusion: Intervention participants showed positive changes in vigorous PA and intake of sugar-sweetened beverages compared to controls, as well as effects on weight-related outcomes at 6 months. Long-term effects were still promising but not statistically significant.