Blackburn defender Shane Duffy scored two first-half own goals and was sent off in injury time as Cardiff won for the first time this season.
Declan John’s 14th-minute shot hit a post and went in off Duffy, before the Republic of Ireland defender headed home Peter Whittingham’s free-kick.
That was his third own goal of the season, having also put through his own net in Saturday’s 3-0 defeat by Wigan.
Danny Graham pulled one back before Duffy was shown a second yellow card.
The former Everton defender was dismissed for kicking the ball at an opponent in the fifth minute of added time.
Defeat for Blackburn was their third in as many Championship matches this season, and they are bottom of the table on goal difference.
They were the architects of their own downfall at a sparsely populated Cardiff City Stadium.
The home side were approaching five and a half hours without a goal when a huge slice of luck came their way with Duffy’s opener.
His misfortune was just beginning, though, and he doubled Cardiff’s advantage by deflected home Whittingham’s free-kick on 20 minutes.
Cardiff forward Anthony Pilkington should have made it three before the break, but he dragged a shot wide, then fired past a post after Lex Immers’ set-up.
Rovers got back into contention when Graham shrugged off Bruno Manga and beat David Marshall at his near post.
And Duffy’s dreadful day was rounded off with an injury-time red card.
Cardiff manager Paul Trollope:
“I’m pleased to get off the mark, even if we made it a bit harder than it should have been. The win will breed confidence, but you can’t relax.
“Maybe for an hour or two, but then attention turns to Fulham on Saturday.
“We were determined to bounce back, but we have been very calm in the group.
“We knew the first win would come, but we have to build and grow from it.”
Blackburn boss Owen Coyle:
“Coming into the club there’s a number of situations I’ve inherited. Shane, Ben Marshall… there have been offers that were rejected a couple of weeks ago.
“But what you have in the modern game is third-party interest, somebody in one ear telling you one thing, someone else in the other ear telling you another.
“They have their heads turned and you’ve got to manage that in the modern game.
“When you step on that field you’ve got to be at your best and be at your maximum and, unfortunately, that’s not happened tonight.”