Issue addressed: There is growing evidence that online parent-focused child healthy lifestyle interventions can improve healthy eating practices and food environments in the home. Greater understanding of whether and how parents engage with these online interventions is needed. This study evaluated the reach, acceptability and impacts of an online parent healthy lifestyle intervention. Methods: A pilot study was conducted in New South Wales during the COVID-19 pandemic when stay-at-home public health orders were in place (July–August 2021). A concurrent mixed methods design was adopted. Data collection measures were: an online participant survey at baseline, post-intervention and 3-month follow-up; two online post-intervention focus groups; and web metrics at post-intervention and 3-month follow-up. Results: There were 181 intervention participants, primarily mothers with high education levels and living in advantaged areas: 43 (24%) completed surveys post-intervention; and of these, 35 (81%; 19% of participants) completed surveys at follow-up. Sixteen mothers participated in focus groups. Parents’ knowledge, self efficacy, role modelling and behaviours improved, but there were no significant differences detected over time. Metrics and survey data indicated webinar recordings, particularly the topics of ‘Fussy Eating’ and ‘Screen time and sleep’, had the greatest engagement and most perceived them as useful (93% and 96%, respectively). Conclusions: An online healthy lifestyle intervention to support parents in providing opportunities for their children to engage in healthier lifestyle behaviours was appealing and acceptable to mothers and has the potential to improve families’ healthy lifestyle behaviours. Enhancing intervention reach amongst fathers and priority populations, as well as incorporating design elements to enhance engagement will be important. So what?: An online healthy lifestyle intervention reached and engaged parents, despite being faced with additional parenting challenges arising from COVID-19 stay-at-home orders. © 2023 The Authors. Health Promotion Journal of Australia published by John Wiley & Sons Australia, Ltd on behalf of Australian Health Promotion Association.