The slide was made specifically for the site and installed sometime around 1989.
But Wellington City Council play spaces specialist Matthew Beres said the potential risk of further injuries has led to the decision to remove it.
"Unfortunately we've had reports of a few serious injuries to some very young children using the slide, and even with signage in place about the rules of use, we've decided this measure is the only way to ensure there are no more incidents like these."
The council has previously agreed a new playground is needed at Frank Kitts Park anyway.
The $6 million upgrade will begin in January.
Social, cultural and economic committee chairwoman councillor Jill Day said the project would refresh the area with all new equipment appropriate for different ages and abilities, including a new slide.
"A new playground will help create wonderful memories of growing up in Wellington for children now and well into the future.
"The new slide will also be just as big and fun, but it will be a tube shape with a twist in the middle designed to reduce speed."
The large slide is currently closed under Covid-19 alert level 3. It will be removed by contractors on Monday, weather permitting.