Pep Guardiola's men have already won the EFL Cup this season and remain in the reckoning for the Premier League and Champions League titles. Unlike last season, when Wigan Athletic stunned City in the cup, they will return to the national stadium in May, too.
Gabriel Jesus appeared to set the tone for the five-time winners with a fine early header, although they were frustrated for the remainder of the first half.
The second period was then surprisingly uncomfortable for City, yet they came through unscathed with the help of one phenomenal Aymeric Laporte clearance to take a big step towards another piece of silverware.
City predictably seized control from the outset and they led after just four minutes as Jesus stooped to meet Kevin de Bruyne's sublime low cross in behind the Brighton defence.
Chris Hughton's side gained a foothold in the match thereafter, though, and Kyle Walker was lucky to stay on the pitch after a heated confrontation with Alireza Jahanbakhsh. The incident was the subject of a VAR review after Walker moved his head towards the Brighton forward, but he escaped with a booking.
Laporte's vital clearance then prevented Glenn Murray from turning Shane Duffy's knockdown into the net early in the second half as an unconvincing City display continued.
Mat Ryan parried two late Raheem Sterling efforts, while the England man was also denied by a Lewis Dunk block, but City were able to see out victory without a second goal.
What does it mean? Another step towards unprecedented success
If City are to win all four major trophies this season, they are going to have to come through some nervy days along the way. This clash was nowhere near as straightforward as it appeared it would be after four minutes, yet Guardiola would take a dozen more outcomes like this between now and the end of the campaign.
Laporte leads the way
Laporte has been one of the standout defenders this season and showed his worth at both ends of the pitch on Saturday. It was the centre-back's gorgeous switch which led to Jesus' opener, before his timely intervention denied Murray at the other end in an excellent individual display.
Walking a tightrope
Considering a relative lack of attacking threat from Brighton down his flank, Walker endured a tough first half. He looked to be set to be substituted after going down with an early injury, only to stay on the pitch and clash with Jahanbakhsh. The England defender was fortunate not to see red and was finally substituted at the break.
Key Opta Facts
- Manchester City have become the ninth different team to reach both major domestic English cup finals within the same season, after Arsenal, Chelsea, Everton, Liverpool, Manchester United, Middlesbrough, Sheffield Wednesday and Tottenham Hotspur.
- Brighton have never won in five competitive matches at Wembley in all competitions, drawing one and losing four.
- City have scored 20 goals in the FA Cup this season, the most by a team in a single season in the competition since Chelsea in 2011-12 (also 20).
- Pep Guardiola has become the first manager to reach both major domestic English cup finals in the same season since Kenny Dalglish with Liverpool in the 2011-12 campaign.
- City are unbeaten in their last six games at Wembley in all competitions (W5 D1), conceding just one goal in those matches.
- Jesus has scored 12 goals in 15 appearances in cup competition this season (FA Cup, League Cup and Champions League) compared to six goals in 25 appearances in the Premier League.
There is no let-up in City's schedule and their next task is a sizeable one: Tottenham away in a Champions League quarter-final first leg on Tuesday. Meanwhile, Brighton's focus returns to a grounding relegation battle as they host Bournemouth next weekend.