<p>Sleep problems in young children are highly prevalent and place children at risk for numerous detrimental child and family outcomes. This pilot study aimed to assess the feasibility of an unguided, parent-focused, online sleep intervention, the Lights Out Online program, in terms of adherence rates, acceptability to parents, and effects on (a) child sleep, anxiety, and behaviour problems, and (b) parental self-efficacy, and parent sleep, depression, anxiety. The study was a pilot, open (uncontrolled) trial with a within-group repeated measures (baseline (T1), 12-weeks post-baseline (T2)) design. Participants were 24 parents <i>(M</i>_<i>age</i> = 36.2, <i>SD</i> = 4.1) of children aged 3–6 years (<i>M</i>_<i>age</i> = 4.1 years, <i>SD</i> = 1.1) with sleep problems. Participants completed an average of 3.58 out of 4 sessions by T2, and parents reported satisfaction with program content and presentation. A series of mixed-effects linear regression models demonstrated significant improvements in child sleep, child anxiety, child behaviour problems, parent sleep, parent anxiety and parental self-efficacy, from T1 to T2. However, significant improvements were not demonstrated for parent depression and parent stress. The results of this study should be taken with caution given the small sample size and lack of control group. However, the study provides preliminary support for the feasibility of Lights Out Online.</p>