England captain Moeen Ali won the toss and decided to bat against Pakistan at the National Stadium in Karachi on Thursday.
England, who are touring Pakistan for the first time in 17 years, will be in a strong position after their first win on Tuesday.
The visitors won the first match of the seven-match series in Karachi by six wickets on Tuesday.
Richard Gleeson, a fast bowler for the visitors, and Mohammad Hasnain, a fast bowler for Pakistan, were both replaced by spinner Liam Dawson.
The final matches of the series will be played in Lahore and Karachi (September 23 and 25). 28 September, 30 September and 2 October