But comments from new boy Andriy Yarmolenko suggest they are only just getting started.
Pellegrini is the highest profile boss in the history of the club, and the only to have had a top flight league title on his CV. It gave West Ham fans new hope after two torrid seasons since moving to the London Stadium.
And they look as good as their word with five signings so far and others soon to be announced.
The excellent free transfers of Jack Wilshere and Ryan Fredericks have joined alongside Issa Diop for a fee rising to £25 million, Lukas Fabianski for £7 million and Andriy Yarmolenko for £17.5 million.
“I know I am the fifth player to arrive at West Ham this summer," Yarmolenko told whufc.com.
"I can see that an interesting project is being built here and that the team has very high aims that they want to achieve.
“That is why I accepted this challenge. It will be interesting for me to take part in the future of this club.”
When Ryan Fredericks signed for the Hammers last month he inadvertently revealed on the club's official website that other top quality players would be following him through the door and he has been proved correct.