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 ef ects of lead using 1% methylene blue as the vital dye for assessment of the l ukes’ 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 l ukes 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.