Leading 2-1 from Thursday’s first leg, the Rams completed a 6-2 aggregate victory with a 4-1 win at the iPro Stadium.
Will Hughes’ first goal since November gave McClaren’s men the half-time lead before further strikes from Chris Martin, George Thorne and Jeff Hendrick sealed the club’s first return to Wembley since the 2006-07 season – when Derby were last promoted to the top flight.
Kazenga LuaLua’s late reply was a mere consolation for Brighton, who tasted defeat in the play-off semi-finals for the second successive year.
Andre Wisdom nearly extended Derby’s aggregate lead early on.
The on-loan Liverpool right-back cut infield and his left-footed shot forced Brighton goalkeeper Tomasz Kuszczak to get down to his left to smother.
Another left-foot strike by Craig Forsyth from the opposite flank skidded off the greasy surface and into the side netting five minutes later.
Albion were dealt a blow in the 24th minute when captain Gordon Greer was forced off injured. The defender was replaced by Adam Chicksen.
Ten minutes later, Derby were in front. Jamie Ward and Forsyth linked up down the left and when the latter sent a low cross into the box, Hughes had timed his run perfectly to sweep a first-time shot into the bottom corner of the net.
The tie might have been all over before half-time had Kuszczak’s clearance rebounded into the net off Ward rather than loop onto the roof of the net.
In the 56th minute, it was over. Martin made it 2-0 with his 25th goal of the season and extended Derby’s aggregate lead to 4-1.
Johnny Russell’s far-post cross was headed back across goal by Ward and Martin beat two Brighton defenders to the ball to poke it over the line from inside the six-yard box.
It saw the former Norwich striker become the Rams’ most prolific scorer since the 1992-93 campaign when Paul Kitson netted 24 times.
The tie was finished but McClaren’s men, roared on by the partying Derby faithful, went looking for more goals.
Only a fine fingertip save from Kuszczak denied Ward on the hour and five minutes later the former Manchester United keeper thwarted Russell.
In a rare spell of Brighton pressure around the midway point of the second half Lee Grant was called upon to keep out Keith Andrews’ 25-yarder and a LuaLua effort.
But normal order was soon restored and a third Derby goal came after 76 minutes courtesy of the laces of Thorne, whose volley from just ouside the area flew into the bottom right-hand corner of the net.
Hendrick rounded off a lovely move with a neat finish three minutes from time but there was still time for another goal – for Brighton.
Lua Lua fired home a low shot from just inside the box after good play down the right.
It was nothing but consolation and Derby will play the winner of the second semi-final between QPR and Wigan, who resume on Monday night at Loftus Road with the tie goalless.