Additional capacity will be available on routes to Crete (Chania and Heraklion), Kos and Santorini.
The extra services, which will fly between July and September, will operate from Birmingham, Leeds Bradford, Manchester and Stansted airports between July and September.
Birmingham will gain an extra Wednesday service to Chania from 1 July to 23 September and extra Thursday services to Santorini from 2 July to 24 September, while Leeds Bradford will get another weekly Kos service on Saturdays starting 4 July and running through to 26 September.
Elsewhere, Stansted's Chania route will gain an extra Saturday service operating from 19 July to 27 September.
Manchester, meanwhile, is getting two extra Heraklion services on Wednesdays and Fridays operating from 1 July through to 25 September. This means Jet2 will operate two daily flights on these days.
In total, Jet2 will operate to 15 Greek destinations this summer, including Samos, which is a new addition for summer 2026.
The programme is its largest ever to Greece with more than 3.5 million seats on sale across 131 routes, including 25 new routes. At peak times, Jet2 will operate more than 360 weekly departures to Greece.
Steve Heapy, Jet2.com and Jet2holidays chief executive, said Jet2 was "stepping in once again to meet demand" from agents' clients and consumers.
"Summer 2026 will be our biggest ever summer programme to Greece, and we are cementing our position as the UK’s largest airline from the UK to sunshine favourite by putting on even more flights," he added.
