We investigated critical belief-based targets for promoting the introduction of solid foods to infants at 6 months. First-time mothers (N = 375) completed a Theory of Planned Behaviour belief-based questionnaire and follow-up questionnaire assessing the age the infant was first introduced to solids. Normative beliefs about partner/spouse (ߠ= 0.16) and doctor (ߠ= 0.22), and control beliefs about commercial baby foods available for infants before 6 months (ߠ= -0.20), predicted introduction of solids at 6 months. Intervention programs should target these critical beliefs to promote mothers' adherence to current infant feeding guidelines to introduce solids at around 6 months.