This study examined the effects of praise for intelligence and praise for effort on Iranian EFL learners' language mindsets, perceived communication competence, speaking anxiety, and willingness to communicate (WTC). The students in three English classes (N = 63, all junior high school students) in a private language institute filled in self-report scales on language mindsets, perceived communication competence, speaking anxiety, and WTC, and then were assigned to praise for effort, praise for intelligence, and control conditions for 14 classroom communication sessions. They answered the same scales in the last session of the experiment. The results of quantitative analysis indicated that praise for effort enhanced learners' growth mindsets, communicative competence, and WTC, and decreased their speaking anxiety. In contrast, praise for intelligence and no praise decreased students' growth mindsets. Praise for intelligence further decreased students' WTC and increased their speaking anxiety. Follow-up qualitative data gathered by interviews with 12 students further suggested that praise for effort facilitated learners' WTC by increasing their growth mindsets and lowering their speaking anxiety. Finally, we discussed practical implications for how language teachers enhance students' success in classroom communication.