ABSTRACT Emerging evidence suggests smartphone use has adverse effects on mother‐infant relationships. However, while research suggests that maternal responsiveness is reduced when using a smartphone, little research has been undertaken with infants. This study used cross‐sectional data to explore associations between infant social‐emotional development, maternal mental health outcomes, smartphone use, and mother‐infant responsiveness. We recruited 450 mothers with infants aged 3–9 months, in the UK. Data were col…