Sterling - the £49million summer signing from Liverpool - has scored six goals for City already this season despite being deployed as a winger.
The 20-year-old reached double-figures for goals scored last term and Pellegrini is confident his attacker can boost that number with additional work.
"I knew he scored eleven for Liverpool, but I don't think that's a huge amount for Raheem," the Chilean coach said of Sunday's trip to Aston Villa.
"He must score more and to do that he must work a lot.
"He soon settled into our style of play and I'm happy that he has six already, but of course Raheem is a young player and I was sure from the beginning that he must improve a lot.
"When you are 21-years-old and you work as a good professional, you must improve. Playing every day with important players is good for a young player, you are always learning from experienced players.
"But the third thing, which is very important, is the style we play is good for him. He will have good chances to score. Now we must be quiet and let him do it in the correct way."
