Linguistic self-confidence is an underlying factor in L2 motivation and positive L2 learning outcomes. However, few studies have investigated its hypothesized relationship to objective L2 learning outcomes or the relationship between self-confidence and cognitive and affective individual differences that influence L2 learning. In this study, participants learned novel L2 words and their grammatical gender; they were then tested on their objective accuracy for recognizing and producing the words and gender. They also completed tasks measuring their subjective perceptions of linguistic abilities (to tap into linguistic self-confidence), L2 motivation, L2 anxiety, and working memory. Subjective perceptions significantly correlated with accuracy at post-test, supporting the hypothesis that learner perceptions are related to actual learning outcomes. Analysis of individual differences showed that only affective factors significantly predicted L2 learning perceptions. These results provide insight into contributions of linguistic self-confidence to L2 learning.