Telephone-based interventions can be effective in increasing child fruit and vegetable intake in the short term (<6 mo). The long-term efficacy of such interventions, however, is unknown.The primary aim of this study was to determine whether the short-term (<6 mo) impact of a telephone-based intervention on children's fruit and vegetable intake was sustained over a longer term. A secondary aim of the study was to assess the long-term impact of the intervention on the intake of foods high in fat, salt, or sugar (noncore foods).The study used a cluster randomized controlled trial design. Parents were recruited from Australian preschools between February and August 2010 and allocated to receive an intervention consisting of print materials and 4 telephone-counseling calls delivered over 1 mo or to a print information-only control group. The primary endpoint for the trial was the 18-mo postbaseline follow-up. Linear regression models were used to assess between-group differences in child consumption of fruit and vegetables and noncore foods by subscales of the Children's Dietary Questionnaire.Fruit and vegetable subscale scores were significantly higher, indicating greater child fruit and vegetable intake, among children in the intervention group at the 12-mo (16.77 compared with 14.89; P < 0.01) but not the 18-mo (15.98 compared with 16.82; P = 0.14) follow-up. There were no significant differences between groups at either of the follow-up periods in the noncore food subscale score.Further research to identify effective maintenance strategies is required to maximize the benefits of telephone-based interventions on child diet.