The ceremony in St Peter's Square will be led by Pope Francis with his predecessor Pope Benedict XVI in attendance.
The Vatican has labelled it an unprecedented event where four pontiffs are symbolically united for the first time.
Millions will be able to watch with around 500,000 in Rome and cinemas across the world hosting showings in 3D. In the UK there will be 45 screenings while Sky television will also broadcast the ceremony.
The two - who will become saints - are both recent popes. John XXIII served between October 1958 and June 1963 and is widely remembered for bringing about the Second Vatican Council, which was set up to address relations between the Church and the modern world.
John Paul II served between October 1978 and April 2005 making him the second longest reigning pope and was also the first non-Italian pope for more than 400 years.
Brother Roy from Gravesend, who's served the Church through a homeless ministry, is taking a group to the event.
He told Premier's Des Busteed on the News Hour of the day he once met Pope John Paul.
Pope Francis has delivered an address to the people of Poland (Pope John Paul II's home country) ahead of Sunday's ceremony.
He said: "I hope that the canonisation of John Paul II, and also of John XXIII, will give a new energy to the daily and persevering work of the Church in your country.
"Some of you will be in Rome but thanks to mass media, many [more] can take part in this great event."
The ceremony will be the first ever double canonisation which was made possible by the confirming of two healing miracles.
Firstly Italian nun Sister Caterina Capitani claimed she'd been healed after receiving a piece of Pope John's bed sheet while suffering from a gastric haemorrhage back in 1963.
Then in 2011 Floribeth Mora Diaz from Costa Rica claimed she'd been healed from a brain aneurysm after looking a photograph of Pope John Paul.
Ted Harrison is the author of the book Tales of Three Popes. He tells Premier how the process of canonisation works.
The event has been marred however by the death of a man who's been crushed to death by a giant wooden crucifix in northern Italy.
Twenty one year old Marco Gusmini, who was on a visit to the Alpine village of Cevo with other young Catholics, was killed instantly.
The monument had been dedicated to Pope John Paul.
Meanwhile the Bishop of Shrewsbury is inviting people to use this weekend to pray for the future generation of priests.
Rt Revd Mark Davies is releasing a pastoral letter which will be read in parishes across his diocese.
It will say: "This Sunday, I ask you to pray for the priests of the future, the priests on whom the future of our Diocese depends.
"I hope that in our time many young men will - like Saint John and Saint John Paul - be ready to respond wholeheartedly to this wonderful calling."