Background: Reproductive-age women are a vulnerable population for HIV infection. The relationship between knowledge and practices is not well described in a context where levels of knowledge, attitudes, and practices about HIV infection are inadequate. Aim: To determine the association between knowledge and practices about HIV infection in Peruvian reproductive-age women. Methods: Analysis of secondary data from the 2019 Demographic and Family Health Survey. It got a probabilistic, stratified, and two-stage sample. We included reproductive-age and actively sexual women. Scores above the upper tertile of the observations were defined as "adequate knowledge" by answering 18 questions. Then, we determined the association between adequate knowledge with each of the five practices. Descriptive and inferential statistics -bivariate and multivariate- were used with the Poisson regression for survey analysis. Results: The mean of correct answers was 12.6 (95% CI: 12.5 - 12.7). 19.2% of Peruvian women had used a condom in the last sexual relationship. An adequate level of knowledge was associated with the use of condoms in the last sexual intercourse (PRa: 1.20; 95% CI:1.06 - 1.36), with having a sexually transmitted infection in the last year, and with having a diagnostic test for HIV infection. Conclusions: Considering a low prevalence of condom use in the last sexual intercourse of Peruvian women of reproductive age, adequate general knowledge about HIV infection has associated with the accomplishment of this practice.