AbstractIntroductionThe corona virus (COVID‐19) pandemic may have a prolonged impact on people's lives, with multiple waves of infections and lockdowns, but how a lockdown may alter emotional functioning is still hardly understood.MethodsIn this 100‐daily diaries study, we examined how to affect intensity and variability of adolescents (N = 159, M_age = 13.3, 61.6% female) and parents (N = 159, M_age = 45.3, 79.9% female) changed after the onset and during (>50 days) the second COVID‐19 lockdown in the Netherlands, using preregistered piecewise growth models.ResultsWe found only an unexpected increase in parents' positive affect intensity after the lockdown onset, but no immediate changes in negative affect intensity or variability. However, both adolescents and parents reported gradual increases in negative affect intensity and variability as the lockdown prolonged. Lockdown effects did not differ between adolescents and parents. However, within groups, individuals differed. The individual differences in the effects were partly explained by life satisfaction, depressive symptoms, and self‐reported lockdown impact.ConclusionsOverall, these findings suggests that a lockdown triggers changes in daily affective well‐being especially as the lockdown prolongs. Individual differences in the effects indicate heterogeneity in the impact of the lockdown on daily affect that was partly explained by baseline life satisfaction and depressive symptoms. However, more knowledge on the causes of this heterogeneity is needed to be able to increase resilience to lockdown effects in the population.