Against a backdrop of angry fan protests against the Venky's Group that has owned Rovers since 2010, Boro struck twice in the opening eight minutes to take control.
Tommy Conway needed less than 90 seconds to beat Aynsley Pears with a fine opener before a deflected strike from Samuel Iling-Junior swiftly followed.
A fifth win in seven lifted Middlesbrough above both West Bromwich Albion and Coventry City and into the play-off places before the rest of the weekend's fixtures, but Blackburn suffered a fifth straight league defeat for the first time since February 2021, with Ismael yet to win in six since replacing John Eustace on February 25.
Socceroos attacking midfielder Riley McGree and former Central Coast and Melbourne City goalkeeper Tom Glover were unused Boro substitutes on Friday night.
Blackburn's first home game since a supporters' group called for the Rovers chief executive, head of football operations and the chief operating officer to stay away from Ewood Park - a request rejected - was played amid sustained chanting against the club's ownership.
The mood only darkened when Boro took the lead before Blackburn had barely registered a touch.
Conway took his 12th goal of the season superbly, receiving Kelechi Iheanacho's pass with his back to goal outside the area and deftly flicking it around Joe Rankin-Costello before firing beyond the helpless Pears.
Six minutes later, it was 2-0. Iheanacho again got the assist, laying the ball off for Iling-Junior on the edge of the box. Danny Batth tried to head it to safety but instead only deflected it beyond Pears in front of the most vocal Rovers supporters.
Blackburn started the second half brightly, with Todd Cantwell narrowly missing the target in the 54th minute.
They were certainly better but the chances kept coming Boro's way. A poor pass from Pears was cut out by Iheanacho before Aidan Morris' powerful shot was blocked, and only a poor cross from Delano Burgzorg denied Conway a tap in after they broke in numbers.
Yuki Ohashi had late chances for the hosts, testing Travers at his near post with a powerful shot before bringing another save out of the Boro keeper with a powerful strike in the dying minutes, but it ended in a defeat that left yet more questions on and off the pitch for those in charge at Ewood Park.
With AAP.
