Unicef says climate change is among the greatest threats to children in the region amid fears that destructive events such as Category 5 tropical cyclones will become the new normal.
The organisation issued the warning to mark Universal Children's Day.
It says climate change is exacerbating and speeding up already existing challenges in low-lying countries such as Kiribati, Tuvalu and the Marshall Islands.
Unicef says this threatens to undo development gains made over decades.
The Pacific region is also home to four of the world's ten most disaster-prone countries - Vanuatu, Tonga, Solomon Islands and Papua New Guinea, many of which are finding the frequency and intensity of natural disasters increasing dramatically due to climate change.