Aardman Animations, the creator of Wallace and Gromit, has designed new character called Pedro the Penguin to appeal to children and parents.
It is also showing support for local businesses as both firms are based in Bristol.
The HL Vantage Junior Isa launches on the 1 November and six million children will be eligible at the outset, including those who were not eligible for a Child Trust Fund. A further 800,000 will be newly eligible from birth.
Children who already have a Child Trust Fund are not eligible for the Junior Isa.
Ian Gorham, chief executive of Hargreaves Lansdown, said: "Pedro the Penguin will help bring the Junior Isa to life and we hope it will encourage parents, grandparents and children to save and invest for their future."
The two versions of the Isa, Cash Junior Isa and Stocks and Shares Junior Isa, will have no capital gains tax, no income tax on savings and no further tax on dividend income. The maximum contribution is £3,600 per year.
Danny Cox, head of advice at Hargreaves Lansdown, said: "Over £15bn was invested into more than £15m Isa accounts in the last tax year.
"If Junior Isas can capitalise on the success of the current Isa, it has the potential to be one for the most successful children's saving schemes of all time."
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