This article analyses ECEC staffs' perspectives on the in-service professional development (PD) process aimed at improving the quality of interaction in ECEC, inspired by the Caregiver Interaction Profile (CIP) scales. The study draws on theories and research on PD and ECEC quality and falls within a pragmatic paradigm, using qualitative individual interviews, thematic analyses and external observations. Main findings: staff found the process highly useful, their motivation increased during the process, they experienced improved autonomy, self-confidence and well-being and became more conscious about different interactional aspects. Staff experienced changes in practice regarding three interactional aspects of the CIP scales, sensitive responsiveness, respect for autonomy and verbal communication. Staffs' reflections are compared to their growth in interaction skills. The findings suggest that the PD process enhanced staffs' interaction competence although significant change only was found for verbal communication three months after the PD process. Implications for practice, limitations and further research are considered.