Introduction: Chemical pesticide is commonly used among vegetable family farmers in Sabah. There is no system to monitor adverse health effects. This study is to determine the blood cholinesterase activity and associated factors among vegetable family farmers. Methods: A cross sectional study has involved 163 farmers aged 18-60 years old. Validated questionnaire was used to assess the associated factors. Lovibond AF267 Cholinesterase Kit was used to determine the blood cholinesterase activity. Chi square test was used to determine the association between blood cholinesterase activity and socio demographic factors and work practices. Results: Approximately 23.3% of study sample had low blood cholinesterase activity. There were significant associations between low blood cholinesterase activity with older age group (p<0.001), lower educational level (p<0.05), longer duration of pesticide exposure (p<0.05), did not attend pesticide safety training, use single pesticide (p<0.05), no specific storage place of pesticide (p<0.05) and not wearing PPE (P<0.05). Conclusion: Nearly one-fourth of vegetable family farmers has low blood cholinesterase activity which is associated with older age, lower educational level, prolonged exposure to pesticide, lack of training and unsafe work practices. There is a need to monitor blood cholinesterase activity and to do training on safe and proper handling of pesticide to protect the health of the farmers and their families.