This paper outlines the development and psychometric evaluation of the Manifestations and Vulnerabilities of Behavioural Insomnia in Childhood Scale (MAVBICS), an instrument intended to assess the manifestations of, and factors underpinning, child behavioural insomnia. The MAVBICS comprises two sections: a more general sleep and bedtime information section (Section 1), and a psychometric measure of six theoretically derived factors that underlie, contribute to, and are manifestations of, child sleep problems (Section 2), that is the focus of this research. Study 1 comprised an exploratory factor analysis of Section 2 items (EFA; n = 328 parents of children aged 3–12 years), with a final 25 items found to load highly onto 6 factors; Sleep Maintenance Problems (4 items, α = 0.88), Co-Sleeping Behaviours (4 items, α = 0.93), Bedtime Routines (5 items, α = 0.82), Bedtime Resistance (5 items, α = 0.88), Bedtime Worries (3 items, α = 0.85) and Bedtime Fears (4 items, α = 0.86). Study 2 comprised a confirmatory factor analysis (CFA) of Section 2 items and tests of convergent validity (n = 313), with results confirming the factor structure and providing evidence for convergent validity through correlations in expected directions between MAVBICS scores and other sleep, anxiety and behaviour measures. Study 3 tested the test–retest reliability of Section 2 items (n = 53), and found support for the temporal stability of the MAVBICS over a 2-week period. Overall, the results provide strong preliminary evidence for the validity of the MAVBICS total score and its subscales, although the Bedtime Routines subscale may be less useful.