Government policies are encouraging older workers to delay retirement, which may curb younger workers' career advancement. We study a Dutch reform that raised the retirement age by 13 months and nearly tripled employment at age 66. Using monthly linked employer-employee data, we show that affected firms delay and decrease replacement hiring, and coworkers' earnings fall via reductions in hours worked, wages, and promotions. Combined, the hiring and coworker spillovers offset most of the additional hours worked by older workers, disproportionately affect career advancement for younger workers and women, and considerably increase the policy's ratio of welfare costs to fiscal savings.