This study investigated the impact of the transition to grandparenthood on employees' psychological involvement in their job, attitude toward retirement, and retirement‐related hopes and concerns, taking into account sex and lineage. The participants were 152 maternal and paternal grandparents who were assessed at 2 time points (approximately 2 months before and 3 months after the birth of their first grandchild) and 76 control participants who completed the same assessments with an interval of 6 months. Both grandmothers and grandfathers were less involved in their job and had more family‐related hopes and fewer retirement‐related concerns about health, finances, and dependence than control participants. The analyses also revealed lineage effects: Maternal grandparents were less psychologically involved in their job and had a more positive attitude toward retirement, in particular fewer fears of uselessness and loneliness, than paternal grandparents.