Hansi Flick's side led 4-0 from the first leg last week, but were quickly under pressure when Guirassy converted an early penalty, before Pascal Gross had a goal disallowed for offside.
Guirassy then pulled another goal back early in the second half, but Dortmund dreams were dashed soon after when Ramy Bensebaini put through his own net from Fermin Lopez's dangerous delivery.
There was still time for Guirassy to complete his hat trick, but it was too little too late, as Barca progress 5-3 on aggregate, despite seeing their 24-game unbeaten run come to an end.
SPORTS MOLE'S VERDICT
With Paris Saint-Germain also struggling tonight away to Aston Villa, the two will still be the red-hot favourites to win the competition, but Dortmund have exposed Barcelona's limitations tonight.
Barca's clinical front three were stifled for most of the evening, as a raucous home support suffocated the visitors, and allowed Dortmund to get back into a tie that looked beyond them.
There was plenty of fortune about Barca's solitary goal of the evening too, coming via an unfortunate own goal, but Flick's side have still shown enough this season to suggest this was just an off-night.
It will be Barca's first semi-final in the competition since 2019, but Flick will hope seeing their lengthy unbeaten run coming to an end will not affect their pursuit of an extraordinary treble.
DORTMUND VS. BARCELONA HIGHLIGHTS
Guirassy pen vs. Barcelona (11th min, Dortmund 1-0 Barcelona)
It is the perfect start for Dortmund, whose early pressure has paid off, with Gross drawing a foul from Wojciech Szczesny in the area, before Guirassy steps up and confidently dinks it down the middle to put BVB on the board in the tie.
Guirassy goal vs. Barcelona (49th min, Dortmund 2-0 Barcelona)
The Yellow Wall is rocking at the Westfalenstadion! A deep, in-swinging corner is met by Bensebaini, who knocks it back into the six-yard area where Guirassy is waiting to nod home from close range, giving the hosts real hope now of the unthinkable!
Bensebaini own goal vs. Dortmund (54th min, Dortmund 2-1 Barcelona)
What a nerve-settler that is for the Catalans! Fermin drives down the right wing and his dangerous cross is diverted into his own net by Bensebaini in a cruel twist of fate for the home side.
Guirassy goal vs. Barcelona (76th min, Dortmund 3-1 Barcelona)
Is there still hope for Dortmund? Great work from Julien Duranville down the right forces Ronald Araujo into a big error that puts an opportunity on a plate for Guirassy to complete his hat trick. The hosts have just 15 minutes to spark an astonishing comeback.
MAN OF THE MATCH - SERHOU GUIRASSY
The Guinean has been Dortmund's player of the season, and he has shown everyone why tonight with an excellent hat trick that was unfortunately in vain for the hosts.
A confident and cheeky penalty got the ball rolling, before he was in the right place at the right time to nod home Dortmund's second, and just when it seemed the tie was beyond them, he gave them fresh life by completing his hat trick with 15 minutes remaining, but Guirassy sadly ends up on the losing side.
DORTMUND VS. BARCELONA MATCH STATS
Possession: Dortmund 46%-54% Barcelona
Shots: Dortmund 18-7 Barcelona
Shots on target: Dortmund 11-2 Barcelona
Corners: Dortmund 8-4 Barcelona
Fouls: Dortmund 14-11 Barcelona
BEST STATS
WHAT NEXT?
Dortmund will look to ensure they return to the Champions League via the league route with some positive results in their final five games of the season, starting with a home clash against Borussia Monchengladbach on Sunday, while Barca continue their hunt for the La Liga title at home to Celta Vigo.
Written by
Andrew Delaney