Welegedara, 32, played the last of his 10 one-day internationals in 2010 and was forced to return home from the Test tour of Australia last year due to a hamstring injury.
He now partners Lasith Malinga, Nuwan Kulasekara, Shaminda Eranga, Thisara Perera and captain Angelo Mathews in a strong seam attack suited to England’s conditions.
Mendis was ignored for the June 6-23 tournament as the selectors opted for the experience of left-arm spinner Rangana Herath and off-spinner Sachithra Senanayake.
The batting will revolve around the seasoned trio of Tillakaratne Dilshan, Kumar Sangakkara and Mahela Jayawardene.
Sri Lanka are drawn with defending champions Australia, New Zealand and hosts England in group A of the preliminary league, with the top two teams qualifying for the semi-finals.
The other group comprises India, South Africa, Pakistan and the West Indies.
Sri Lanka open their campaign against New Zealand in Cardiff on June 9.
Sri Lanka’s squad:
Angelo Mathews (capt), Dinesh Chandimal (vice-capt), Tillakaratne Dilshan, Kusal Perera, Kumar Sangakkara, Mahela Jayawardene, Lahiru Thirimanne, Jeevan Mendis, Thisara Perera, Lasith Malinga, Rangana Herath, Nuwan Kulasekara, Shaminda Eranga, Sachithra Senanayake, Chanaka Welegedara.