Vector borne diseases, such as malaria, cause direct impacts on the health and indirect impacts on the productivity and labor supply of workers. While the biological process by which malaria is transmitted is well understood, the economic impact of malaria on people’s daily functioning is less well known primarily because of the simultaneous determination of health and labor supply. This study analyzes the effects of malarial infection on sugarcane cutters’ earnings, labor supply, and productivity as they are randomly assigned malaria testing and treatment over time through a mobile health facility at a large sugarcane plantation in Nigeria. We find a significant and substantial intent to treat effect, but program effects are strongest in the survey round where there is the highest malaria prevalence. The offer of a workplace based malaria testing and treatment program in the first survey round increases worker monthly earnings by 7%, indicating that treated workers have 7% higher monthly earnings than sick workers. Productivity gains explain over half of the earnings effect suggesting that productivity loses due to malaria may be significantly underestimated in previous studies which only account for labor supply effects of illness. In the second survey round, lower malaria prevalence reduces statistical power which reduces the precision of our estimates.