Early relational health is a key determinant of childhood development, while relational trauma in the parent-infant dyad can instigate a cascading pattern of infant risk. Fortunately, early relational trauma is detectable and modifiable. In 2018, Australian Maternal and Child Health (MCH) nurses participated in MERTIL (My Early Relational Trauma-Informed Learning), a program to identify and prevent relational trauma. Program evaluations revealed nurses felt competent and confident to identify and respond to relational trauma; however, response capacity was inhibited by inadequate parent referral options. In response, MERTIL for Parents (My Early Relational Trust-Informed Learning) was developed, which is an online, evidence-based, self-paced parenting program that focuses on enhancing parental knowledge of relational trust and its significance for infant development. This low-cost, accessible prevention resource targets emerging relational concerns to reduce later service system engagement. The potential for universal preventative online programs that target parental and relational wellbeing remains under-explored. This paper reports on a protocol for implementing a MERTIL for Parents pilot study describing practitioners' and parents' perspectives on program feasibility and efficacy. This study is a mixed methods, parallel armed, uncontrolled, repeated measures design. We aim to recruit 48 Australian MCH practitioners from the states of Victoria and New South Wales. These professionals will in turn recruit 480 parents with a child aged 0-5 years. All parents will receive MERTIL for Parents, which entails a 40-minute video, tipsheets, posters, and support resources. Parent data will be obtained at three periods: pre-program, program exit, and program follow-up. Practitioner data will be collected at two periods: pre-parent recruitment and program follow-up. Data collection will occur through surveys and focus groups. Primary parent outcomes will be socioemotional assessments of program efficacy. Practitioners and parents will each report on program feasibility. This protocol describes the feasibility and efficacy of a new online parenting program, MERTIL for Parents, with pilot field studies commencing in March 2023. We anticipate that this resource will be a valuable addition to various child and family services, for use in individual support and group work.