The study aimed to compare the effectiveness of a suite of implementation strategies of varying intensities on centre-based childcare service implementation of nutrition guideline recommendations at 12-month follow-up. A six-month three-arm parallel group randomised controlled trial was undertaken with 69 services, randomised to one of three arms: high-intensity strategies (executive support; group face-to-face training; provision of resources; multiple rounds of audit and feedback; ongoing face-to-face and phone support); low-intensity strategies (group face-to-face training; provision of resources; single round of audit and feedback); or usual care control. Across all study arms, only three high-intensity services were compliant with overall nutrition guidelines. A significant group interaction was found between the three arms for compliance with individual food groups. Relative to control, a significantly greater proportion of low-intensity services were compliant with dairy, and a significantly greater proportion of high-intensity services were compliant with fruit, vegetables, dairy, breads and cereals, and discretionary foods. No significant differences between the high- and low-intensity for individual food group compliance were found. High-intensity implementation strategies may be effective in supporting childcare service implementation of individual food group recommendations. Further research is warranted to identify strategies effective in increasing overall nutrition compliance.