Each year, sealers kill hundreds of thousands of seal pups in commercial slaughters. Shot or clubbed to death mainly for their fur, they die cruelly. Some are left wounded and suffering, and others, skinned alive. HSI campaigns in particular against commercial seal slaughter in Canada and Namibia.

Canada's annual commercial harp seal hunt is the largest slaughter of marine mammals on Earth. Sealing is an off-season activity for fishermen who typically earn only a fraction of their incomes from it. Seals are not overpopulated, nor are they jeopardizing the Canadian cod fishery. Seal product trade bans and HSI's Canadian seafood boycott are increasing pressure to end the hunt. HSI supports a government license buyout for fishermen and promotion of ecotourism.

In Namibia, tens of thousands of Cape fur seal pups are killed annually; but economic alternatives could bring far more money to local communities than commercial sealing does.