Swansea will be looking to protect their lead but Brentford were extremely unlucky in the first leg and we think they'll turn things around on home soil with a 2-0 win to book their place in the final.
Brentford will face either Cardiff or Fulham in playoff final.
Ollie Watkins canceled out Swansea's advantage in the opening minutes and Emiliano Marcondes doubled stylish Brentford's lead before the break.
If sending the place off had threatened to overshadow Brentford's performance, the players - between a route-one smash-and-grab, two team triumphs and Pontus Jansson's defensive howler - went some way to sum up what the club is now made of: the old second-tier simplicity and a knack for creating their own hard luck, but clinical, tenacious, scintillating football, too.
Successive defeats against lowly Stoke and Barnsley at the end of the regular season ruined third placed Brentford's hopes of automatic promotion to the Premier League. "The message was we needed to start faster than we ever started before".
Stepping up for Thomas Frank's men during that run was Saïd Benrahma with six goals, including a hat-trick against Wigan (his second treble of the campaign).
Collapsing onto the pitch at the final whistle, the celebrations weren't of a team that is used to a procession towards its glories.
'Because we were just on it.
It has proved a successful formula and Brentford are now just one win away from a lucrative ￡70 million (US$91 million) place alongside Chelsea, Liverpool and company in the Premier League.
Griffin Park, which famously has a pub on each corner, has served as the club's ground for 116 years and always kept a touch of intimacy and authenticity amid the sprawling urbanisation in west London and the rise of state-of-the-art stadiums across England.
Watkins burst through from Mathias Jensen's low pass through the Swans' central defence to calmly slot under keeper Erwin Mulder for his 26th goal of the season.
Brentford had been too conservative in the first leg, but they were surging forward with poise and objective this time and doubled their lead in the 15th minute.
Once again Jensen started the move, finding Said Benrahma who lifted the ball on to the head of Marcondes to guide home.
Brentford hadn't won a single play-off match in 11 previous attempts dating back to 2002.
Mokotjo, who has not featured in a matchday squad for the Bees since 30 June, played no part in either leg of the clash against Swansea, and his long-term future at the club remains in doubt.