In research on parental involvement and teacher professionalization, counseling parents on the support of their children's learning processes is considered to be an increasingly important competence area of teachers. However, to date little research has been conducted on the development of appropriate approaches to the assessment of teachers' counseling competence. The current study describes the validation of a behavior-based instrument for the assessment of teachers' counseling competence including counseling talk simulations with standardized parents as well as the examination of its suitability as an intervention for the improvement of participants' counseling competence. The validation was carried out within the framework of a longitudinal quasi-experimental study with 51 prospective teachers. Multivariate repeated measures MANOVAs revealed the suitability of the counseling talk simulations both as an assessment instrument and an intervention. Results provide numerous implications for teacher preparation and continuing education, for example, the use of the counseling talk simulations as a didactical tool within the framework of teacher training programs.