Jeremie Bela bagged the only goal of the game late in the first-half, in what was a lively encounter.
Blues rode their luck at times, with Brentford twice hitting the woodwork, but all in all it was a resolute and determined performance from the hosts in their opening 2020/21 Championship fixture.
Goalkeeper Andreas Prieto was missing from the Blues matchday squad because of a calf injury.
Neil Etheridge was on the bench having only made the switch to Blues from Cardiff City 24 hours earlier, meaning that teenage stopper Zach Jeacock was given his first senior start for the Club. There was also a debut for Spanish winger Ivan Sanchez.
Lukas Jutkiewicz returned to the starting line-up after recovering from a quad injury and Gary Gardner was on the subs’ bench after recovering from a knee injury.
On a sun-drenched afternoon at the St. Andrew’s Trillion Trophy Stadium, Blues made a bright start and just six minutes in Bela cut in from the left and let fly with a curling shot which was turned behind by Luke Daniels in the Brentford goal.
Two minutes later the visitors were forced into an early change after Mathias Jensen limped off with an injury to be replaced by Emiliano Marcondes.
Blues were making it difficult for Brentford to play their passing game by closing them down quickly.
But Brentford were not far away from opening their account just before the quarter of an hour mark after Canos did superbly to cut in from the left-flank before sliding the ball across the six-yard box.
Mbeumo tried to stab the ball home but it was blocked by George Friend and trickled through to Jeacock who was able to dive on it.
Brentford were beginning to find their rhythm and Dasilva was inches away from scoring after his shot from distance struck this inside of Jeacock’s far post and bounced away.
At the other end of the pitch Jon Toral saw his difficult volley deflected behind for a corner and then Kristian Pedersen’s header was blocked by Toney.
Mbeumo should have done much better after he was presented with a great opportunity inside the Blues box, but he lashed the ball over the bar from 12 yards.
But it was Blues that actually broke the deadlock after 37 minutes courtesy of Bela.
Sanchez whipped in a corner and Bela directed home a close-range header just inside the near post.
With the half-time whistle on the horizon, Blues had to be thankful to Harlee Dean after the defender headed the ball away from inside his own area. In the process of going for the ball he absolutely clattered Norgaard, but the referee adjudged that the collision was accidental.
In the final seconds of the half Blues won a free-kick in a dangerous position just a couple of yards outside the Brentford area. Jutkiewicz's initial attempt was blocked by the defensive wall and then the striker shot well over.
Half-time: Blues 1 Brentford 0
Blues began the second-half positively and Maxime Colin provided a great cross from the right which Dean headed wide.
Jutkiewicz then tested Daniels in the Brentford goal, before Canos hit the Blues bar with an overhead kick for the visitors.
Just after the hour-mark Jeacock did superbly to deny Marcondes after Pedersen had headed the ball straight to the Brentford man. Marcondes' goalbound header was saved by Jeacock, and then the Blues stopper blocked a second attempt and deflected the ball behind for a corner.
Mbeumo then went incredibly close after he was played in behind the Blues defence. But as Jeacock narrowed his angles, the Brentford player fired the ball just a shade past the far post.
As Blues began to tire, Karanka made two substitutions in the space of eight minutes with Dan Crowley replacing Jon Toral and Adan George being sent on for Sanchez.
With 10 minutes of normal time remaining Brentford were looking to attack in numbers, but a well-organised Blues defence was standing firm.
After Pedersen headed the ball behind for a corner, Brentford had a great opportunity with just a few minutes of normal time remaining.The ball was sent in and Jensen headed the ball down into the ground and over the bar.
Blues: Jeacock, Colin, Pedersen, Friend, Clayton, Jutkiewicz ((0+2), Bela, Dean, Sanchez (George, 75), Toral (Crowley, 67), Sunjic.
Subs not used: Etheridge, Roberts, Kieftenbeld, Dacres-Cogley.
Bookings: Sunjic (59), Pedersen (72), Clayton (80).
Goals: Bela (37).
Brentford: Daniels, Henry, Pinnock, Norgaard, Canos (Forss, 72), Jensen (Marcondes, 8 (Fosu, 78)), Dasilva, Toney, Jansson, Mbeumo, Dalsgaard.
Subs not used: Balcombe, Thompson, Goode, Fosu, Zamburek.
Bookings: Norgaard (49)
Referee: Tony Harrington.