This study investigated the extent to which second language (L2) learners benefited from proactive form-focused instruction (FFI) targeting French grammatical gender attribution and the degree to which L2 learners' attention control and working memory predicted their learning gains. A total of 102 L2 learners received either proactive FFI targeting French grammatical gender attribution or their regular instruction (i.e. control condition) for six 80-minute instructional sessions. A pretest, an immediate posttest, and a delayed posttest were administered, each entailing binary-choice, text-completion, picture-description, and listening tasks. The L2 learners also completed the Simon Test and the Corsi Block-Tapping Test, which measured their attention control and working memory. Results showed that L2 learners receiving the proactive FFI condition significantly outperformed those receiving the control condition in all tasks after the instructional sessions. More importantly, L2 learners' attention control and working memory were significant predictors of their learning gains in the binary-choice and listening tasks, but not in the text-completion and picture-description tasks. The current study highlighted the roles of L2 learners' attention control and working memory in proactive FFI.