Canterbury have held on to the Ranfurly Shield with a thrilling 33-28 win over Bay of Plenty at Te Kaha Stadium in Christchurch.

It was their first defence - after they beat Otago last weekend - but it was looking decidedly shaky with 14 minutes to go when the scores were locked at 28-28.

It had been 21-7 to Canterbury at halftime, the holders notching three tries after having a decided edge in possession and territory.

Bay of Plenty scored just before halftime from a tap penalty, but their challenge looked to be going backwards when Ngane Punivai scored for Canterbury early in the second half.

But the momentum shifted big-time with the Steamers roaring back into the game, scoring three tries to level up the scores.

Canterbury hit back with a try to Toby Bell with 10 minutes to go and then had some nervous moments after a try by Andrew Knewstubb was ruled out.

Bay of Plenty mounted a sustained attack taking the game into added time before a knock-on sealed their fate.