Pazzini took just 25 seconds to score with a rasping long range effort that took a slight deflection off Anton Ferdinand and flew past goalkeeper Lee Camp.
Tickets for the first football match to be played at the rebuilt stadium sold out within hours of their having gone on sale.
Though only about two-thirds of the seats at the 90,000-capacity national ground were filled - Wembley is being tested to get its safety certificate - the FA said it was still the "largest ever U-21s crowd in world football history."
The FA were given the keys to Wembley earlier this month after work on it was finally completed, years behind schedule and at a final cost of 800 million pounds.
The March 24 match is the second of two "ramp-up" events to ensure the stadium is in working order, the first being a March 17 community day.