OBJECTIVES: To explore barriers for recruitment, attrition, and mHealth usage in a Swedish randomized controlled trial (RCT) including a mobile health (mHealth) intervention for children 5 to 12 years (n = 79) in obesity treatment.

METHODS: A retrospective process evaluation was conducted using Normalization Process Theory (NPT). To answer the study objectives, data on staff- and parental mHealth experience and usage, staff working time, recruitment, and reasons for attrition were evaluated in relation to the NPT constructs.

RESULTS: Recruitment process was complex and trial enrollment during the summer decreased staff- and participant-engagement. Attrition was influenced by technical issues, lack of motivation, and disliking the mHealth intervention. The major barrier for mHealth usage was technical problems. Staff struggled understanding core intervention components and found the intervention time consuming.

CONCLUSION: Based on our findings we suggest future enablers for sufficient recruitment, retention, and increased mHealth usage of value for conducting pediatric obesity trials.