Early childhood is an ideal time for interventions to address the development of unhealthy weight gain; understanding why interventions do/do not work is essential for developing new and effective programs. This study was a process evaluation of a parent-based preschooler obesity prevention intervention (MEND 2-4) and aimed to: (1) investigate the program-related opinions of participants; (2) understand the support and resources used, and barriers to creating a healthy home environment; and (3) explore parents’ perceptions regarding raising a preschool child within a healthy home environment. Participants were 20 randomly selected intervention group parents who took part in a randomised controlled trial evaluating the efficacy of MEND 2-4. Each parent completed one semi-structured phone interview about their thoughts and experiences related to MEND 2-4, and questions regarding the establishment or maintenance of healthy behaviours and attitudes around creating a healthy home environment for themselves and their preschool-aged child. Interviews were reviewed for common responses and qualitatively analysed using Interpretive Phenomenological Analysis. Support and resources identified by parents as useful for helping the establishment/maintenance of healthy dietary and physical activity behaviours included facilities and activities, family, media, and other people, hampered by lack of time, work pressures, and insufficient knowledge. Findings suggested that similar interventions should incorporate practical strategies, provide ideas and tools that are applicable to real world situations, allow parents and children time to learn together and separately, and provide follow-up sessions. When exploring the concept of a healthy home environment parents wanted to meet the needs of their child within their stage of development in conjunction with their own needs, recognised the importance of eating well and being physically active from an early age, and identified barriers across both the macro and microsystems of their child’s environment. Future preschooler obesity prevention interventions should consider these issues.