Vasectomy is used less often than female sterilization, and many men who do not want more children may lack accurate information about vasectomy. Between May and June 2018, we used a nationally representative online panel to survey U.S. men between 25 and 55 years of age who did not want more children about their vasectomy knowledge. We also asked about interest in undergoing the procedure if it were free or low cost and explored whether a paragraph addressing common misperceptions was associated with interest. We assessed characteristics associated with high vasectomy knowledge (≥3 accurate responses to four questions about vasectomy’s effect on sexual functioning and method efficacy) and vasectomy interest, using chi-square tests and multivariable-adjusted Poisson regression. Of 620 men surveyed, 564 had complete data on the outcomes and covariates of interest. Overall, 51% of respondents demonstrated high vasectomy knowledge. Men who knew someone who had a vasectomy were more likely to have high knowledge (prevalence ratio [PR]: 1.50; 95% CI [1.22, 1.85]). One-third of the sample (35%) said they would consider getting a vasectomy. Men with high (vs. moderate/low) knowledge were more likely (PR: 1.36; 95% CI [1.04, 1.77]) to consider getting a vasectomy. Race/ethnicity, income level, and receiving the informational paragraph were not associated with vasectomy interest. Greater vasectomy knowledge affects men’s interest in the procedure. Given that many U.S. men lack accurate knowledge, efforts are needed to address misinformation and increase awareness about vasectomy to ensure men have the information they need to meet or contribute to reproductive goals.