Larkin, FionnualaOostenbroek, JanineLee, YujinHayward, EmilyFernandez, AmyWang, YingMitchell, AlexLi, Lydia YMeins, Elizabeth2023-11-232023-11-232023-11-15Child Development, ISSN: 0009-3920 (Print); 1467-8624 (Online), Wiley. doi: 10.1111/cdev.140390009-39201467-8624http://hdl.handle.net/10292/16999The efficacy of a smartphone app intervention (BabyMind©) in facilitating mind‐mindedness was investigated in a randomized controlled trial, assigning mothers and their 6‐month‐olds (<jats:italic>N</jats:italic> = 152; 72 girls, 146 White) to intervention or active control conditions. Mothers who had received the BabyMind© app intervention scored higher for appropriate (<jats:italic>d</jats:italic> = .61, 95% CI .28, .94) and lower for non‐attuned (<jats:italic>d</jats:italic> = −.55, 95% CI −.92, −.18) mind‐related comments at follow‐up (age 12 months), compared with their control group counterparts. Adjusting for missing data did not alter this pattern of findings. Mothers' baseline parental reflective functioning did not moderate these relations. Results are discussed in terms of the benefits of early intervention and exploring the efficacy of the app in more diverse populations.© 2023 The Authors. Child Development published by Wiley Periodicals LLC on behalf of Society for Research in Child Development. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.http://creativecommons.org/licenses/by/4.0/1701 Psychology1702 Cognitive SciencesDevelopmental & Child Psychology3904 Specialist studies in education5201 Applied and developmental psychologyJournal ArticleOpenAccess10.1111/cdev.14039