The Mood and Feelings Questionnaire (MFQ) is widely used for the assessment of depression in adolescents. The main aim of this study was to examine the concurrent and predictive validity of a composite of four MFQ items related to suicidal ideation using an interview measure of suicidal ideation. A prospective 3-wave high-risk study of offspring of parents with recurrent depression was used including 294 families where children were initially aged 9–17 years. Measures included four parent and child rated MFQ items assessing suicide-related ideation (referred to here as the “MFQ-SI”) and a clinically-defined interview measure of suicidal ideation. A parent-child combined MFQ-SI subscale performed well as a screening tool against the interview measure of suicidal ideation (baseline AUC (95% CI):0.92 (0.85–1.00)). Longitudinally, this measure showed reasonable predictive validity against future suicidal ideation (AUC (95% CI):0.73 (0.58–0.88)). Lastly, there was evidence that a child-rated MFQ-SI scale performed better than a parent-rated one in detecting concurrent suicidal ideation. Longitudinally, both parent and child scales showed reasonable predictive validity against future suicidal ideation. In summary, a brief screen using four MFQ items related to suicidal ideation performs well in identifying concurrent and future suicidal ideation in high-risk adolescents.