The 24-year-old France midfielder, glad the protracted battle over his move was over, signed a four-year deal at the world's richest club with local media reporting the transfer fee was around 25 million pounds.
"It's a big relief because it was a long, long negotiation and discussion between the two clubs," Nasri, who was chased for most of the close season, said on the City website.
"Now I'm finally a City player. That's what I wanted since the start.
Keen to wrest the Premier League title from their more successful neighbours Manchester United, City have spent an unprecedented amount of money for British football in putting together a team that on paper is up to the challenge.
It was that potential that attracted Nasri to the club with the midfielder saying compatriot and former City player Patrick Vieira had told him it was "the club of the future".
Nasri, who will wear the number 19 shirt, was one of the final pieces in the puzzle for coach Roberto Mancini who said this month that if he completed his squad in this transfer window City could fight for the title this year.
"He's a fantastic player because he has technique and mentality," Mancini said in a video on City's website on Wednesday.
"I knew him when he was playing at Marseille because I followed him when I was at Inter [Milan], we wanted to talk to him five years ago. In the last four years he has improved a lot."
Mancini has spoken of his frustration over the time it has taken to bring Nasri to the North-West of England, saying he wanted to bring him in earlier to prepare for the season.
His new signing shared his annoyance.
"I was a little bit frustrated because I said to the [Arsenal] manager I wanted to leave," Nasri said.
"So I stayed for the whole pre-season, I wanted to do the pre-season with Manchester so I could know my team mates a little bit more."
PERFECT START
Nasri, who scored 15 goals for Arsenal last season, could make his City debut on Sunday when his new club travel to face his old club's bitter North London rivals Tottenham Hotspur.
Mancini will have to work out how to fit Nasri into a team who already boast another playmaker, David Silva, and attacking talent such as Sergio Aguero, Edin Dzeko, Carlos Tevez and Mario Balotelli.
"He's a player maybe like David Silva. But he can also play in the middle," the Italian, who has hinted he has not quite finished shopping in this transfer window, said.
With City gearing up for their first Champions League campaign when the group stage starts next month, Mancini has plenty of chances for squad rotation.
City had already laid out around 50 million pounds in this window on Argentina forward Aguero, French left-back Gael Clichy - also bought from Arsenal - and Montenegro defender Stefan Savic.
Since being taken over by the Abu Dhabi United Group in August 2008, City have splashed out on a series of high-profile signings and results on the field have steadily been improving.
Under Mancini, who took over as manager in late 2009, they were third last season, one place above Arsenal in City's highest Premier League finish. They also won the FA Cup, their first major trophy in 35 years.
City have enjoyed a perfect start to the new Premier League season by winning both games to top the table on goal difference ahead of champions and neighbours Manchester United.
Nasri's exit was another blow to Arsenal who have endured a torrid start to the season, including former captain Cesc Fabregas' departure for Barcelona earlier this month.
