Methodological challenges associated with measurement reactivity and fatigue were addressed using diary data collected from mothers (n = 47), fathers (n = 39), and children (n = 47; 8-13 years) across 56 consecutive days. Demonstrating the feasibility of extended diary studies with families, on-time compliance rates were upward of 90% for all family members, with only minor within-person declines in weekday compliance over time. Multilevel models revealed slight decreases in mother and father daily reports of parent-child conflict and warmth across days, suggesting possible measurement reactivity. Global perceptions of parent-child involvement, measured via a 1-time survey at baseline, moderated change in parent, but not child, diary reports of conflict and warmth. Finally, weakening agreement between mother and child diary reports of conflict and strengthening of positive within-person associations between child-reported negative mood and same-diary ratings of parent-child conflict indicate potential fatigue-related declines in response accuracy. Although generally minimal, observed measurement effects highlight the need for additional methodological research in the study of everyday family life.