The impact of chronic exposure to pesticides, especially among farmworkers, continues to be an area of research interest, especially in developing countries. This study aimed to measure and compare levels and profiles of pesticides in farm environments and farmworkers in an agricultural area of Mexico, as well as their effects in this cohort. Organochlorine and organophosphate pesticides were measured in soil and water samples from farms in the Navolato Valley, Sinaloa, Mexico. Levels of these pesticides as well as transaminases, alkaline phosphatase, acetylcholinesterase and hemoglobin were also measured in blood and urine from farmworkers of the study area and compared with levels in a control population. All 17 target organochlorine pesticides and four of nine target organophosphate pesticides were detected in soil and water samples. In farmworkers, 14 of 17 target organochlorine pesticides and seven of nine organophosphate pesticides were detected. Pesticide profiles were similar in farmworkers as in the environment. In comparison, only six organochlorine pesticides and three organophosphate pesticides were detected in control population, in much lower concentrations and with lower detection frequencies. Clinical analyses indicated that levels of transaminases and alkaline phosphatase were elevated while levels of hemoglobin and acetylcholinesterase were depressed in farmworkers compared to the control group. The results indicate that farmworkers are suffering from chronic exposure to workplace pesticides and could endure adverse health effects.