The average sergeant salary at Napa County was $299,593 , which is 1 percent lower than the average salary for this job in California, but 113 percent higher than the national average for this job . Sergeant salaries at Napa County typically range from $293,409 to $331,398 (25th to 75th percentile). The highest reported sergeant salary was $457,804. There are 14 employees at Napa County with the job title sergeant.