Members of Manx National Heritage and the National Trust of Guernsey will be eligible for free entry to sites in both jurisidctions.
It comes following the two charities reaching an agreement ahead of an 'air bridge' which allows flights between the two Islands later this month.
Manx visitors will be able to go to the Folk and Costume Museum at Saumarez Park, and the mid-19th-century Les Caches Farm.
Meanwhile, members from Guernsey will be able to visit eight sites here for free, including the likes of Castle Rushen and the house of Manannan.
Crogga still owes the Isle of Man Government money
DoI says works at Liverpool ferry terminal will take longer
Over 50 employment tribunals outstanding at the DoI
Free period products bill raises cost concerns for MHKs
Key road in Ramsey to re-open early this afternoon
Want to start training to become a nurse?
Appeal launched after fly-tipper filmed dumping rubbish
Prepare your pets for Bonfire Night, says Manx charity
