Pulisic has scored three goals in five games since the Premier League restarted last month amidst the coronavirus pandemic, helping keep Chelsea in pole position for a place in the Champions League next season.
The United States international endured a slow start to life in England after moving to Chelsea from Borussia Dortmund last summer, but he is now proving to be one of the club's most important players.
Asked about the 21-year-old's influence over the past month, Lampard said: "He's hugely important because he's got great talent. We know that.
"Earlier on in the season, at the start, he came here, difficult conditions in terms of [he] hadn't really had a break early in the season, but he started to play really well for us, and now he's moved his game on another level, not just in how he's going by people but real end product.
"Look around at the top attacking players in the world, and they score goals regularly to win games, and at the moment, he's doing that, so I'm delighted with him."