Ivorian powerhouse Yaya Toure and Edin Dzeko combined to set up Spaniard David Silva before halftime at St James' Park, while Argentine Aguero added a second in injury time after his first effort was saved.
While the performance was far from vintage, City manager Manuel Pellegrini will be pleased with the three points after last week's 3-0 Community Shield loss to Arsenal indicated his side may have some early season rust.
Earlier, last season's runners-up Liverpool eased past a stubborn Southampton 2-1 as goals from Raheem Sterling and Daniel Sturridge either side of Nathaniel Clyne's thunderbolt ensured the post-Luis Suarez era at Anfield got off to a positive start.
On Saturday, Manchester United began life under Louis van Gaal with a disappointing 2-1 defeat by Swansea City while Arsenal needed a stoppage time Aaron Ramsey goal to beat Crystal Palace 2-1.
Tottenham Hotspur, Hull City and Aston Villa were other opening-weekend winners while Chelsea play at promoted Burnley on Monday.

Latest News from Sports News Desk