Whereas some evidence exists that math anxiety may interfere with math performance from the very beginning of primary school, no study to date has attempted to investigate whether math anxiety may also interfere with early math learning (i.e., the encoding of new math knowledge) and not only with recalling already mastered contents in test situations. Across 2 experiments carried out in 2 different countries (Study 1: N = 115, conducted in Italy; Study 2: N = 120, conducted in the United Kingdom), we addressed this question by presenting 6-year-old children with 2 math contents that had not been covered by their school curriculum before the study. Children were tested immediately before and immediately after the learning phase, and after a 1-week delay. Longitudinal models revealed that math anxiety was negatively related to initial level of knowledge in the case of 3 out of 4 math contents. More importantly, math anxiety was also negatively related to rate of learning in 2 out of 4 tasks (1 task in Study 1 and 1 in Study 2). These studies provide the first evidence that math anxiety may reduce the encoding of novel math contents in memory in very young children, potentially leading to cumulative gaps in math proficiency for children with math anxiety from the very beginning of their formal education.