Peer assessment (PA) is one of the central principles of formative assessment and assessment for learning (AfL) fields. There is ample empirical evidence as to the benefits for students' learning when AfL principles are implemented. However, teachers play a critical role in mediating the implementation of intended policies. Hence, their experiences, beliefs, and attitudes towards PA are important factors in determining whether the policy is actually carried out. A survey of over 1500 primary, secondary, and higher education teachers in Spain elicited their beliefs and values around PA as well as other aspects of formative assessment; only 751 teachers provided complete responses to all PA items. Teachers reported occasional use of PA in their classrooms but with positive experience of it. The vast majority did not use anonymous forms of PA and half of the teachers considered the students were accurate when assessing peers. Confirmatory factor analysis and structural equation modeling were used to examine relationships of attitudes and beliefs to self-reported frequency of using of PA. The self-reported frequency of using PA was strongly predicted by teacher experience of PA which included positive reasons for using PA, rather than negative obstacles for avoiding, prior use, and beliefs that students should participate in assessment, and willingness to include PA in grading.