Geologically, Jeløya is largely made up of a young lava rock-type from the Permian period.
Other islands in the Oslofjord formed during that same time period include Revlingen, Eldøya, Missingene and the Søsterøyene.
The largest Norwegian moraine from the Ice Age crosses Jeløya, goes to the east of Moss and Rygge and continues through Sweden to Finland.
Moss Verft was a shipyard formed in 1870 which was active in shipbuilding until 1987 and was historically one of the biggest employers in the municipality.
Jeløya is today best known for its beaches, its scenery, a swarming harbor with boats, and Refsnes Gods, a hotel with a renowned cuisine.