Objective: This study aimed to assess the knowledge of puerperal mothers about the Guthrie test. Methods: A total of 75 mothers who sought primary care between October 2014 and February 2015 were investigated. The form was applied by the main researcher and the data was analyzed, using descriptive statistics with Microsoft Office Excel, and Statistical Package for Social Sciences (SPSS) programs. Association tests and statistical power were applied.Results: Among the 75 mothers, 47 (62.7%) would have liked to receive more information about the newborn screening, especially regarding the correct sample collection period, followed by the screened morbidities. Most participants (n=55; 85.9%) took their children to be tested between the third and the seventh day of birth, as recommended by the Brazilian Health Ministry. Fifty-four women (72%) were unable to name the morbidities screened by the test in Minas Gerais, and they were also unaware that most have genetic etiology. The health professional who informed the mother about the Guthrie test was mainly the physician. This information was given prenatally to 57% of the cases, and to 43 % at the time of discharge from the hospital. The association test showed that mothers with higher education have more knowledge about the purpose and importance of the Guthrie test. The statistical power was 83.5%.Conclusions: Maternal knowledge about the Guthrie test is superficial and may reflect the health team’s usual practice.