Aim <p>This research study aims to add to the emerging evidence on the potential value of trauma-informed practice (TIP) training programmes for multi-agency practitioners by examining the associated impact of a UK TIP training programme on practitioner attitudes and knowledge, 6 months post training.</p> Subject and methods <p>Participants completed pre- and 6-month post-surveys using four of the five subscales of the Survey for Trauma-Informed Systems Change. Multi-agency participants from across Merseyside (<i>n</i> = 152) completed pre-surveys, engaged in four TIP training sessions and followed with a post-6-month survey.</p> Results <p>Analyses of the pre-post study indicate that a four-session TIP training programme for public services and education staff can significantly enhance the individual-level knowledge and attitudes of trainees regarding trauma-informed practices [pre-mean 76.4, post-mean 90.9; <i>p</i> &lt; .001; large effect size (d = 1.4)]. Engagement in the training programme was associated with a substantial significant improvement in trainees' understanding of brain physiology and biology in connection to trauma, attachment, and ACEs, as well as their awareness of trauma-informed practices. Further, there were significant improvements in trainees' system-wide attitudes, training, support, interaction, and the environment, assessing safety and acceptance.</p> Conclusion <p>This study enhances understanding on the influence of TIP training on multi-agency partners including education, health, police, and the public services. However, this training needs to be supported by wider system changes that have clear leadership for embedding a trauma-responsive system, taking into account staffing levels, staff wellbeing, burnout levels and trainees' personal experiences of ACEs/trauma.</p>