Alonissos has a number of offshore islets that are a popular day-trip destination by boat. Set in the marine park and island nature reserves in their own right, some have restricted access to the public.
Peristera, the scarcely inhabited islet easily seen offshore on the east coast, was once joined to Alonissos and is graced with some nice sandy beaches that are usually empty.
The place is a popular haunt of barbecue boats in the high season and a cantina sets up on the main beach. Recently underwater archaeologists discovered an ancient wreck off the island.
Pelagos or Pelagonissi, is also sometimes called Kyra Panagia after the monastery that lies to the easy. It is a hilly islet with two deep bays.
Gioura is dramatically rocky with precipitous cliffs and is specially protected as its underwater caves are the main habitat of the Monk Seal. It also harbours a rare species of wild goat and a remarkably beautiful cave in the interior, reputed to be the original dwelling of the mythical Cyclops.
Psathoura is small and flat with the remains of an ancient city sunk beneath the waves to the east. In the north is a large lighthouse, built in the last century by the French.
Piperi, is normally closed to visitors as it is the most important habitat for the Monk Seal, Eleonara's Falcon and several rare plants. Piperi has a precipitous rocky shoreline.
Skantzoura has a series of low hills on shores of white marble that create a dazzling azure seabed along the shoreline. There is an abandoned monastery at its centre.