Between 2010 and 2015, Eswatini conducted mass media health behavior campaigns (HBCs) designed to avert new HIV infections. Using longitudinal data from the nationally representative Swaziland HIV Incidence Measurement Survey of 2011, we describe the impact of exposure to HBCs on selected HIV risk behaviors and HIV incidence among sexually active, HIV-negative adults (n = 11,232). Exposure to partner reduction HBCs was significantly associated with reporting fewer (i.e., 1 versus 2, or 2 versus ≥ 3) sexual partners in the prior 6 months at baseline among women (aOR = 3.02; 95% CI 1.38, 6.62); and at both baseline and at 6-months follow-up for men (aOR = 2.26; 95% CI 1.49, 3.44; aOR = 1.95, 95% CI [1.26–3.00], respectively). Despite these reported partner reductions, there was no association between HBC exposure and prospectively observed HIV seroconversions (n = 121). This analysis strengthens the evidence that HIV prevention at the population level requires integrated strategies.