BACKGROUND:Fathers are underrepresented in parenting and child health research. Given there is a strong link between fathers' parenting behaviour and children's well-being, there is a need to find ways to engage fathers more consistently. The current short report provides information and learnings about recruiting fathers online using social media. Results are drawn from an Australian study that aimed to recruit roughly equal numbers of mothers and fathers to participate in a survey about employment, parenting, and health, using online advertising. METHODS:First, a series of five Facebook advertising campaigns were run, aimed at "parents" generally (i.e., gender-neutral). A lack of recruited fathers prompted a second series of six Facebook campaigns aimed solely at fathers. All campaigns targeted employed adult parents of children (≤18 years) in Australia using Facebook's "Adverts Manager." RESULTS:The 11 campaigns recruited a total of 1,468 fathers. The vast majority of these fathers were recruited using the advertisements specifically aimed at fathers (n = 1,441). Gender-neutral campaigns inviting and selecting "parents" to participate in the study overwhelmingly yielded samples of mothers. Similarly, advertisements inviting both "mums and dads" resulted in very low recruitment of fathers. CONCLUSIONS:The extremely low numbers of fathers recruited using the gender-neutral "parent-focused" campaigns was unexpected. Potential reasons for this include low engagement with gender-neutral parenting terms, and/or that mothers were disproportionally exposed to the Facebook advertisements. These learnings suggest that father-focused recruitment is required to target and engage fathers in parenting research and services.