Purpose: The purpose of this paper is to describe the development of new interactive, bi-lingual Sex and Relationships Education (SRE) resources called Tyfu i Fyny/Growing Up, suitable for students aged between five and 12 years. It also discusses the evidence used to support the development of the resources, the support provided for teachers and parents and an initial evaluation following their use. Design/methodology/approach: Tyfu i Fyny/Growing Up are interactive bi-lingual (Welsh and English) SRE teaching resources for primary schools suitable for students aged five to 12 years. These resources comprise of two components, an interactive electronic web-based programme and a floor mat illustrating a naked boy and girl. The electronic web-based programme is used to introduce puberty changes, loving relationships, conception, pregnancy and birth and is suitable for students aged nine to 12 years. The floor mat is suitable to be used with students aged between five and 12 years. Teaching activities can include naming body parts, discussing gender differences, personal safety, distinguishing between appropriate and inappropriate touching, discussing puberty changes and other health promotion activities as well as delivering aspects of the National Curriculum for Wales. Findings: The results from the initial evaluation undertaken with year six students and teachers demonstrates how the resources have impacted on the teaching and learning experiences of primary teachers and students. It also demonstrates how the teacher training sessions and using the Tyfu i Fyny/Growing Up resources have increased teachers' confidence in delivering SRE. Practical implications: The learning experiences of students and their enjoyment of using the Tyfu i Fyny/Growing Up resources were significantly high. The implementation of teacher training improved teaching practice and increased teachers' confidence in the subject. The resources have facilitated the delivery of effective whole school comprehensive SRE programmes for primary schools. These factors confirm the value of the investment given to their development. The resources could easily be customised in line with diverse ethnic, cultural, linguistic and religious requirements. Originality/value: This paper demonstrates how the Tyfu i Fyny/Growing Up interactive SRE resources have influenced the teaching and learning experiences of primary school teachers and students.