Anyone going on a Saga holiday or cruise in 2021 must be fully vaccinated against COVID-19.
The UK tour operator, which specialises in holidays for the over-50s, said it wanted to protect customers' health and safety.
The firm said it would delay restarting its travel packages until May to give customers enough time to get jabs.
People over 50 in the UK have been rushing to book holidays as vaccinations boost confidence.