Background Hepatitis B-linked liver cancer disproportionately affects Hmong Americans. With an incidence rate of 18.9/100,000, Hmong Americans experience liver cancer at a rate that is 6–7 times greater than that of non-Hispanic Whites. Serological testing for the hepatitis B virus (HBV) is a principal means to prevent liver cancer deaths through earlier identification of those at risk. Methods Academic researchers and Hmong leaders collaborated in the design, conduct, and evaluation of a 5-year randomized controlled trial testing a lay health worker (LHW) intervention to promote HBV testing among 260 Hmong adults through in-home education and patient navigation. Results Intervention group participants were more likely to report receiving serological testing for HBV (24% vs. 10%, p=0.0056) and showed a greater mean increase in knowledge score (1.3 vs. 0.3 points, p=0.0003) than control group participants. Multivariable modeling indicated that self-reported test receipt was associated with intervention group assignment (odds ratio [OR] 3.5, 95% confidence interval [CI] 1.3–9.2), improvement in knowledge score (OR 1.3 per point, 95% CI 1.02–1.7), female gender (OR 5.3, 95% CI 1.7–16.6), and having seen a doctor in the past year at baseline (OR 4.8, 95% CI 1.3–17.6). The most often cited reason for testing was a doctor’s recommendation. Conclusions LHWs were effective in bringing about HBV screening. Doctor visits and adherence to doctors’ recommendations were pivotal. Participation of health care providers is essential to increase HBV testing. Impact LHWs can significantly increase HBV screening rates for Hmong, but their doctors’ recommendation is highly influential and should be pursued.