Pellegrini ended his first season in England with two pieces of silverware after City added their second top-flight crown in three years to the Capital One Cup they claimed back in March.
But the unflappable Chilean will not allow his players to rest on their laurels and has vowed to drive them on to further success at home and abroad.
With the title celebrations going on all around him on the pitch at the Etihad Stadium, Pellegrini told Sky Sports: "Big teams cannot be satisfied just with one title.
"It is very important that we have won two titles in the year, we must celebrate today and tomorrow. On Tuesday we will start working for next season, because for the club and the players it is so important."
Pellegrini was happy to savour his achievement of claiming glory in his first season in the Premier League, but paid tribute to his players to adapting to his philosophy and sticking with it even during some tough times during the early stages of the season.
He added: "This was a special season for us, because we have not been at the top of the table because we had games postponed and we didn't start very well.
"One of the most important things we did this year was when we finished playing our sixth game away and we had just four points from 18.
"I told the players we have to change (the results), but we have to play this way, because I think it's the way you must play.
"They believed in me and they continued playing and I think from then until the end we are the team with the most points playing away.
"They are a very special group; they were in a difficult moment when I arrived here. They always believed what I tell them, the way I play, the way I like.
"It is very special because in my first year here in England it is not easy. But I think that I manage a great group of players, a great institution and great fans.
"When you achieve the title the whole year comes down to the hard work that we did during the difficult moments of the year, but I think that this was the best team in the Premier League."
Pellegrini took time out to pay tribute to captain Vincent Kompany, who scored the second goal to sink West Ham after Samir Nasri's opener, and midfielder Yaya Toure who has found the net 20 times in the top-flight this term.
He said: "He (Kompany) had a difficult time after Liverpool, but I think that today he recovered and he was one of our best players over the season.
"It has been a very special season for Yaya. It is not normal for a midfielder to score so many goals, but Yaya plays free in that position with cover from Javi Garcia."