Introduction: Exposure to naphthalene is associated with many toxic effects in humans and laboratory animals. Aim of work: To assess the clinical and laboratory changes among workers occupationally exposed to naphthalene during manufacturing of naphthalene balls. Materials and Methods: This study was conducted on fifty workers in naphthalene balls manufacturing factory. They were compared with fifty non-exposed individuals. Full history was taken and clinical examination was performed. Complete blood picture, reticulocyte count and G6PD activity, urinary naphthalene, albumin and α1 microglobulin in urine were measured in both groups. Environmental assessment of naphthalene in air at workplace was done. Results: The level of urinary (1- and 2-naphthol), urinary albumin and urinary α 1-microgloblin were significantly higher (p< 0.001) among the exposed group compared to the control one. Hemoglobin levels and hematocrit percentage were significantly decreased (p< 0.001) among the exposed group compared to the control. A statistically significant positive correlations among exposed workers were found between the level of urinary (1-and 2-napthanol) and each of duration of employment, urinary albumin and α 1-microgloblin . There were a statistically significant negative correlation between urinary (1 and 2-napthanol) and hemoglobin level. The geometric means of the measurement of naphthalene at workplace were 100 mg/m3 which exceeded the occupational exposure limits according to Egyptian Environmental law (50 mg/m3). Conclusion: Occupational exposure to naphthalene leads to increased risk of health hazards with possible renal and hematological impairment. Therefore environmental control measures and good work practices are recommended at the workplace.