OBJECTIVES: To estimate annual productivity loss costs attributable to being overweight or obese in working adults with asthma patients in the US. METHODS: Working asthma patients (18-64 years old) were identified using the 2003-2009 Medical Expenditure Panel Survey (MEPS).  Asthma patients were identified by self-reported diagnosis, Clinical Classification Codes of 128, or ICD-9-CM code of 493 and the identified patients were classified as normal-weight (18.5≤BMI<25), overweight (25≤BMI<30), and obese (BMI≥30). Productivity loss costs, which were measured based on missed work days due to illness or injury for one year and the hourly wage, were estimated using a two-part model to adjust for patients with zero costs. To estimate the productivity loss costs attributable to being overweight or obese, costs were estimated by assuming every patient is overweight or obese (i.e., treating the indicator variable as equal to 1) and re-estimating by assuming every patient is normal (i.e., treating the indicator variable as equal to 0). Then, the mean differences between the two estimated costs were considered the productivity loss costs attributable to overweight or obesity in asthma patients. All costs were converted to 2011 US dollars using the Consumer Price Index. RESULTS: Annual average productivity loss costs attributable to obesity were $697(95%CI:$614-$780) per patient, 45% higher than overweight (at $480, 95%CI:$397-$563) and 92% higher than normal (at $363, 95%CI:$298-$428). The productivity loss costs in working asthma patients increased as patients were obese, older, or female. Also, the productivity loss costs attributable to overweight or obesity in working asthma patients were estimated at $89 (95%CI:$87-$91) or $250 (95%CI:$246-$254) per person per year, respectively.  CONCLUSIONS:  The productivity lost costs attributable to overweight and obesity in working US adults with asthma were substantial. To reduce the economic burden of treating asthma patients and enhance productivity, this study further highlights the importance of weight control.