Meazza was born in Porta Vittoria, Milan. Having lost his father in 1917 during the tragic fighting of World War I at the age of seven, young Peppe grew up in Milan with his mother, Ersilia who came from Mediglia, helping her sell fruit at the market. He began playing football at six years old.
His nickname, "il Balilla" ("The Little Boy"), was given to him in 1927 by his older teammate Leopoldo Conti, who thought "Peppìn", in Milanese dialect, who was only 17 when he joined the senior team, was too young to be associated to the senior team, and was surprised after Inter coach Árpád Weisz decided to give Meazza his debut for Inter in his place. The Opera Nazionale Balilla, the Fascist youth organisation which collected all children aged 8 to 14 years, was established in 1926 and so Conti thought it was a good way to showcase the young rookie. Meazza scored two goals on his debut in a 6–2 win against Milanese Unione Sportiva in the Coppa Volta in Como, leaving Conti speechless. The Italian Sports Newspaper "La Gazzetta dello Sport" praised his game as "intelligent, fresh, quick", the day after his official debut in the Italian championship, on 12 September 1927.