The objectives of this study are to investigate chromosomal aberrations of snakehead fish in a leachate-affected reservoir located 100 meters from a municipal landfill which compared to non-affected reservoir. Three snakehead fish were collected and chromosomal aberrations were studied using kidney tissue. Lead and mercury were measured in water, sediment and snakehead fish from the affected reservoir at three sampling sites. The results showed that the average concentrations of lead and mercury in water were 0.0012±0.0003 and 0.0053±0.0036 mg/L, respectively. The average concentrations of lead and mercury in sediment were 3.3650±2.1930 and 0.0890±0.0272 mg/kg, respectively. These values did not exceed the standard for water and soil quality except for the mercury in the water, which was higher than acceptable. Lead was not found in snakehead fish from either reservoir. The average concentrations of mercury in snakehead fish from both reservoirs were 0.1330±0.0792 and 0.1180±0.0350 mg/kg, respectively, which were higher than the standard for mercury contamination in food. This study showed that the accumulation of mercury in snakehead fish was higher than in sediment because it accumulates in organisms through the consumption hierarchy. The diploid chromosome number of snakehead fish in both reservoirs was 2n = 42 and the percentage of chromosomal breakages of snakehead fish in the affected reservoir was higher than the non-affected reservoir. There were four types of chromosomal breakages: single chromatid gap, isochromatid gap, single chromatid breaks and isochromatid breaks. The difference in percentage of chromosomal breakages in snakehead fish from both reservoirs was statistically significant (p<0.05).