Brentford took the lead in the 42nd minute when Konstantin Kerschbaumer's clever back-heel found Canos whose low drive beat Cardiff goalkeeper Allan McGregor.
The Spaniard has really shone since rejoining Brentford in January, with the 20-year-old scoring his fourth goal in as many games.
The opening goal had been coming with the Bees' stylish football: Jota's shot was deflected inches wide and McGregor somehow managed to keep out Yoann Barbet's bullet header.
All of Brentford's dominance in the latter stages of the first half was undone shortly after the break when Sean Morrison drew Neil Warnock's hosts level. The Bluebirds skipper rose highest to head home Peter Whittingham's corner in the 47th minute.
In a second half where chances were limited, Whittingham hit the winner in the 76th minute after connecting well with Kenneth Zohore's knock down.
Cardiff had Jazz Richards to thank when his sliding tackle stopped Alan McCormack from bearing down on goal late on, and Warnock's men suffered a late scare when Lasse Vibe's deflected shot hit the side netting.
Smith was understandably unhappy with the result, saying: "I'm very frustrated because it's a game that we were in total control of and could've scored a bit more in the first half.
"We scored a great goal and I expected us to go on and win two or three nil.
"The game had a pre-season feel to it, it was flat and there was no zip."
Warnock revealed that a half-time dressing-down inspired the Bluebirds to beat Brentford, with the manager saying: "I thought it was a decent game. It was a drab first half and we had to change things because I would've fallen asleep.
"Brentford had more possession but I thought we created the better chances. It's disappointing when you go a goal down but I was pleased with the turn around.
"It's very difficult to get myself up for games when I know we are safe. I need an edge on my games, as well.
"So fair play to the lads for taking on board what was said and making an issue and game of it in the second half.
"It's quite easy at this time of the year to go through the motions, but I want fans to go home and talk about the goals and saves."