These seasonal roles will assist with the extra parcels and mail expected to be processed over the festive season, including Black Friday and Cyber Monday.
The temporary positions include 12,000 mail centre sorting roles in England, 2,000 in Scotland, 600 in Wales and 400 in Northern Ireland.
Royal Mail is also looking to fill 3,000 delivery and collection roles and 2,000 temporary HGV and MGV driver roles across the country.
The seasonal workers will be stationed in two parcel hubs, four seasonal parcel sort centres and 37 mail centres across the UK.
Royal Mail’s interim chief operating officer, Jamie Stephenson, said: “As we do every year, we will be pulling out all the stops to make Christmas special for our customers.
“It’s the busiest time for us, and we work tirelessly behind the scenes, planning months in advance, to ensure everything runs smoothly.
“We’re investing heavily in extra resources, including thousands of seasonal team members, to help make sure every delivery arrives on time and with care.”
The company is encouraging applications from people looking to earn extra income for the festive season, with no previous experience required.
The roles offer competitive pay rates and the opportunity for longer-term work.
Royal Mail has also announced plans to add 6,800 hire vans to its fleet of 48,200 vehicles to support this year’s seasonal campaign.
More than 1,200 road haulage contractors are also being hired to transport the festive mail and parcels across the country.