Objectives: This study aimed to investigate changes in the smoking rate among Korean adults from 1998–2009 by gender and occupational groups. Methods: Using the data from the first (1998), second (2001), third (2005) and fourth (2009) waves of the Korean National Health and Nutrition Examination Survey (KNHANES), we examined men and women between 25–64 years old. Occupational groups were classified into 3 groups of non-manual workers, 5 groups of manual workers and other workers groups. The other group included the unemployed, students and housewives. Age-adjusted prevalence rates of cigarette smoking were calculated for 10-year age groups in each wave of the KNHANES. Trends in the smoking rate according to occupational groups were estimated. Results: Among male workers, decreasing trends in smoking rates were observed in non-manual workers, manual workers, and other workers. The odds ratios and prevalence ratios for the smoking rates of the manual workers comparing the non-manual workers increased from 1998 to 2005, whereas decreased to 1.38 and 1.12, respectively, in 2009. Differences in smoking rates between manual and non-manual workers increased from 1998 to 2005 but decreased from 2005 to 2009. Among female workers, the smoking rates decreased between 1998 and 2001 and increased beginning in 2001. Conclusions: The smoking rate of the manual workers group was still higher than that of the non-manual workers group. Anti-smoking programs specific to each occupational group are needed.