Lloyd Dyer's close-range effort gave City, who started the day in fourth, a 16th-minute lead, which David Nugent's penalty doubled on the stroke of half-time.
Blackburn undeservedly pulled one back through Jordan Rhodes's 70th-minute spot-kick, but the Foxes followed up Saturday's 2-0 defeat of FA Cup holders Wigan, a result also completed by a Nugent penalty, while Rovers suffered their third loss of the season.
The hosts were buoyed earlier in the day by signing Poland defender Marcin Wasilewski, previously a free agent after leaving Belgian champions Anderlecht, on a one-year deal.
Wasilewski was not available for this match but midfielder Matty James was after suspension, although he stayed on the bench throughout. Sean St Ledger was still sidelined.
Blackburn were without midfielder Lee Williamson, who was sent off in the fiery Lancashire derby against Burnley at the weekend, while experienced midfielder David Dunn remained out with a knee injury.
City had an early penalty appeal turned down when right-back Ritchie de Laet dribbled into the Rovers box and his cross hit Tommy Spurr's upper body.
But the hosts went ahead when the influential Andy King threaded through to Dyer, who prodded across Jake Kean from just to the left of goal.
Leicester continued to dominate and their captain Wes Morgan had a goal-bound header from a corner blocked by Kean.
Blackburn responded with a period of pressure, although they did not have a clear-cut chance to show for it.
That proved costly when just before the break Rovers defender Jason Lowe conceded possession in midfield, which led to de Laet gaining possession on the right of the box where Spurr fouled him.
Following lengthy Blackburn protests, Nugent buried the spot-kick high down the middle of goal. Kean was then booked for further complaints, as was Corry Evans for a foul on Dyer.
Jamie Vardy spurned a golden chance to make it three early in the second period when Anthony Knockaert put him one-on-one with Kean, who saved. Knockaert then tested Kean from the right of the box before Rovers skipper Scott Dann saw yellow for checking Dyer.
Kean kept out a rasping drive from King and a close-range shot by Nugent before Danny Drinkwater was booked for an indiscretion in his half.
Blackburn were handed a lifeline when Spurr played in substitute Chris Taylor, who was brought down by Drinkwater in the left of the box. Rhodes coolly slid the penalty into the left corner, sending Kasper Schmeichel the wrong way.
Dann's far-post header from Tom Cairney's left-sided free-kick forced a save from Schmeichel with 10 minutes to go. Dann needed treatment after but continued.
Late on City's Chris Wood had an effort ruled out for off-side and Vardy hit the near post from the right of the box as Leicester ended strongly, although Cairney fired just wide late on.