With the Magpies desperate to return to the Premier League as soon as possible, the 41-year-old's advice is worth listening to.
The former Magpie had a long career with his boyhood club, spending 20 years at St James's Park, before leaving in 2013.
He went on to turn out with Hull in the Premier League in recent seasons, before helping out at Sunderland as third choice goalkeeper last season.
Harper was in the Newcastle squad the last time they were in the second tier in 2010, playing 45 times as they won the title.
And, with many expecting the Magpies to dominate the Championship under Rafa Benitez the 41-year-old, Harper was quick to urge a little bit of caution ahead of the beginning of the season.
“There are some good signs there," he told Talksport.
“They’ve lost Georginio Wijnaldum and the Championship is a tough league but they’ve made good signings and they’re rightly favourites – but it won’t be easy.
Alexis Sanchez scores the third goal for Arsenal as Hull's Steve Harper looks on
“I’ve seen some daft bets that they will go the season unbeaten but there needs to be a bit of realism."
For the goalkeeper, the manner of which the club escape the division isn't important this season, with it clear the most important thing is returning to the Premier League as quickly as possible.
“It will be tough for Newcastle but they just have to get out of that league," he said. "Whether they win it, come second or go up through the play-offs.
Newcastle manager Rafael Benitez
“We won it last time and people think it was easy because we won it by a dozen points or so but it wasn’t, it was tough.
“You have to be streetwise and clever, hopefully Newcastle can be those things and get out of the Championship at the first attempt.”
The Magpies aren't the only Premier League regular who are in the Championship this season, with Aston Villa also relegated in the spring. With plenty of strong sides all desperate to earn promotion, Harper's advice to be smart in how they tackle the division is well worth taking on board.