City have won eight of their last nine matches in the Premier League, while Alan Pardew's side have lost their last two in the top flight.
But Pellegrini has warned against complacency, insisting they will face a severe test on Tyneside.
"Of course it will be a real fight," he said.
"Newcastle in the last two games have lost, but when they lost against Arsenal one or two weeks ago they were playing very well and they were fighting for the first position in the table.
"In the FA Cup they lost at home against Cardiff but I am sure that playing at home they will be a very difficult team."
City thrashed West Ham 6-0 at the Etihad Stadium in the Capital One Cup semi-final in midweek and have also put six past Arsenal at Eastlands this season.
Tottenham were thrashed 6-0 and Norwich 7-0 in Manchester, while champions Manchester United went down 4-1 and Newcastle themselves lost 4-0 there on the opening weekend.
But Pellegrini has insisted no one in the Premier League can be taken for granted, especially as they face the Magpies away from home.
"It always seems the opposition are not very good when you score so many goals but, I repeat, there are no easy games in the Premier League," he added.
"Maybe when you finish the game you might think it was easy because we played very, very well, but not all the games will be exactly the same.
"Maybe playing exactly the same we might score only one or two goals. It is very important to improve in all senses as a team."
Watch Newcastle take on Manchester City live from St James' Park at 1.30pm this Sunday on Sky Sports 1 and Sky 3D.