Introduction: Diabetes Mellitus (DM) is the eleventh most important cause of premature mortality in Egypt and is one of the most prevalent and costly chronic disease conditions in Egypt, it is associated with a profound negative impact on workers’ productivity. Aim of work: To assess the impact of diabetes on the productivity of the workers in construction industry. Materials and Methods: A case-control study was conducted among 34 diabetic workers in construction industry and 34 healthy workers from the same site. Health and performance questionnaire (HPQ) was used. In addition, some questions about socio-demographic characteristics, medical and occupational characteristics. Investigations were done including: fasting and post prandial blood sugar, HbA1c, liver and renal functions, body mass index (weight / hight²) were calculated, control group was matched for socio demographic and occupational characteristics. Results: work days lost due to DM/month ranging from 0-12 and partial loss of work days due to DM/month was 0-3 ,a statistically significant difference between diabetics and controls (where controls were better than diabetic workers) regarding work performance of an average worker, total score of work performance and percentage of total score (P0.05). There was no significant difference between mean value of days lost due to DM and that of days lost due to other reasons (P>0.05). Conclusion: our results provide evidence for a negative impact of diabetes on work productivity among construction workers in Egypt due to increased time loss, increased absenteeism (either partial or total work days loss), yet, the increased performance by the diabetic workers compensated for that loss. Further studies are recommended to explore the consequences of diabetes on work place and to suggest the interventions.