The present work investigates how the increased domestic responsibilities created by the Spring 2020 lockdown of the COVID-19 pandemic in Norway and gender ideologies relate to the well-being of mothers with elementary school children. In June 2020, we conducted a cross-sectional online study including current and retrospective measures with 180 mothers (Mage = 39.96 years, SD = 6.11) of elementary school children across Norway. First, in line with earlier research on the strain of the pandemic on parents, and especially mothers, we found that Norwegian mothers’ well-being during the lockdown significantly declined compared to before the lockdown (both measured retrospectively). Furthermore, mothers’ well-being after the Spring 2020 lockdown did not immediately return to pre-lockdown levels. Finally, we predicted that gender ideologies (i.e., essentialist beliefs about parenthood) would exacerbate the negative impact of increased domestic responsibilities (i.e., childcare and housework) on mothers’ well-being (i.e., higher standard-higher stress hypothesis). As predicted, for mothers who more strongly endorsed the belief that mothers are instinctively and innately better caretakers than fathers, perceptions of increased domestic responsibilities were associated with lower well-being post-lockdown. These findings point to the specific challenges mothers face in times of crisis, and the importance of addressing and confronting seemingly benevolent ideologies about motherhood that place additional burdens on women.