Teachers' attitudes and beliefs toward student behavior can have a profound effect on how students in their classroom are viewed. This study investigated teachers' perceptions of code-mixing, or the use of two or more languages in speech, by bilingual and emergent bilingual learners in their classrooms. One hundred and twenty-eight PK-12 teachers in the U.S. rated statements about students' code-mixing. Results indicated that while teachers had positive views about code-mixing in general, they had more negative ratings for statements related to the effect of code-mixing on student performance and why students code-mix. Findings also revealed that having bilingual and/or English as a second language credentials are the only factor among other demographic and background variables that significantly predicts positive views on code-mixing. This study contributes to the literature on teacher beliefs and attitudes about their bilingual students who engage in this language practice.