The 23-year-old flew in from his homeland and was taken to City's Carrington training ground where the player is expected to undergo a medical before further negotiations are held.
However, it is not anticipated Aguero's personal terms - reported to be a five-year contract worth about ?200,000 a week - will be a stumbling block for cash-rich City who are backed by the wealth of Sheikh Mansour, a member of Abu Dhabi's ruling family.
City's previous record transfer was Robinho, who arrived from Real Madrid for ?32.5million as the new owners made him their marquee signing to signal their intent just days after taking over in August 2008.
The Aguero deal is believed to be closer to ?38million, the value of the buy-out clause inserted in the new contract he signed with Atletico Madrid in January.
"Just arrived in Manchester to finalise the details of signing with City," Aguero wrote on Twitter.
"Everything is going very well! I'll tell you more in a while."
With City striker Carlos Tevez adamant he wants to leave to be nearer his wife and two daughters in Argentina Aguero is seen as the ideal replacement.
Younger than his compatriot by four years, the Atletico star has been a prolific goalscorer in La Liga and that is why he became one of the most sought-after strikers in Europe.
Atletico had resigned themselves to the fact they would lose their prized asset when he announced in May, before he departed to play for Argentina in the Copa America, that he wanted to leave.
Aguero's preference was to remain in Spain, with city rivals Real seemingly the most likely destination, but Atletico were keen to resist such a move.
So an offer from Manchester City, although Italian club Juventus were also interested, represented a better option for the Madrid side.
Atletico coach Gregorio Manzano admitted last night that Aguero's departure looked imminent.
"It seems as though in the coming hours we will have a final outcome to the issue that has has occupied us for so long," he told Spanish radio station Cope.
"It is already in it's final stretch, I've asked the players to focus on Thursday's game (a Europa League tie against Stromsgodset).
"Unfortunately we won't be able to call on Kun (Aguero)."
Source: Team Talk
Source: Team Talk