Objective: To evaluate the effects of lead in the morphology and viability of Fasciola gigantica (F. gigantica) (giant liver fluke) isolated from infected livers of carabaos in vitro using the following concentrations of lead: 0, 100, 150 and 200 mg/L. Methods: In vitro viability and motility assay was conducted to evaluate the effects of lead using 1% methylene blue as the vital dye for assessment of the flukes' viability. Results: Results indicate that F. gigantica can tolerate lead exposure as high as 200 mg/L with visible morphological variations. Upon exposure to lead, liver flukes tend to curl and excrete black precipitates as a sign of physiological stress response. Furthermore, the lethal concentration (LC50) of lead against F. gigantica in vitro was 160 mg/L. Conclusions: In conclusion, tolerance of liver flukes to high levels of lead suggests its potential as a possible biomarker of environmental pollution.