Background: Early relational health is a key determinant of childhood development, and 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 pilot study describing nurses’ and parents’ perspectives on program feasibility and efficacy. Methods: This study is a mixed-methods, parallel-armed, uncontrolled, repeated measures design. We aim to recruit 28 MCH nurses who will in turn recruit 480 parents with a child aged 0-5 years. All parents will receive MERTIL for Parents entailing a 40-minute video, tipsheets, worksheets, and support resources. Parent data will be obtained at three periods: pre-program, program exit, and program follow-up. Nurse data will be collected at two periods: parent recruitment completion and program follow-up. Data collection will occur through surveys and focus groups. Primary parent outcomes will be socioemotional assessing program efficacy. Nurses and parents will each report on study program feasibility. Discussion: This protocol describes the feasibility and efficacy of a new online parenting program, MERTIL for Parents, with pilot field studies commencing in July 2022. We anticipate that this resource will be a valuable addition to various child and family services, for use in individual support and group work.