Background: Family-based assessments of risk factors for adolescent emotional, behavioral, and substance use problems can be used to identify adolescents who are at risk and intervene before problems cause clinically significant impairment. Expanding traditional methods for assessing risk, this study evaluates whether "lability," referring to the degree to which parent-adolescent relationships and parenting fluctuate from day to day, might offer additional value to assessment protocols aimed at identifying precursor risk factors. Methods: This study sampled 151 adolescents and caregivers, collecting data at a baseline assessment, a 21-day daily diary protocol, and a 12-month follow-up assessment. Daily diary data were used to calculate within-family lability scores in parenting practices, parent-adolescent connectedness, and parent-adolescent conflict. Results: Regression analyses evaluated whether lability predicted adolescent's depression, anxiety, antisocial behavior (ASB), drunkenness, and marijuana use at 12-month follow-up. Lability in parent-adolescent connectedness, accounting for baseline levels, gender, age, and initial levels of outcomes, was associated with risk for depression, anxiety, ASB, drunkenness, and marijuana use. Lability in parenting practices also was associated with risk for depression, anxiety, and drunkenness. Baseline levels moderated some of these effects. Parent-adolescent conflict lability was only associated with depression. Conclusions: These findings provide evidence for substantial value added when including dynamic assessments of family lability in predicting long-term adolescent risk outcomes and call for integration of dynamic methods into assessment practices.