Valentino was a private person of few words. On 15 March 1942 he married Emilia Rinaldi, whom he had two sons, both players: Sandro - who played for Inter Milan and the Italy national team – and Ferruccio (who was named in honour of the president of Torino, Ferruccio Novo), born respectively in 1942 and 1945. In Turin he lived in a small apartment in Via Torricelli 66. He worked in Lingotto and reported as a FIAT worker essential to wartime production, to avoid participating directly in the Second World War. Although the Torino players salaries were very good, they were not considered exaggerated, compared to normal payroll. The players were not considered professionals and officially held other jobs; in the aftermath of the war, Mazzola owned a sports shop in Turin, where he sold footballs that he manufactured personally.
It was during this time at Venezia that Mazzola first met Ezio Loik, who had moved to the club from Milan. They debuted together in the 1942 game Italy played against Croatia and won 4–0. Both were very different, although they came from very humble backgrounds: Fiume-born Loik was quiet and somewhat defensive, while Lombard Mazzola was much more impulsive and friendly. Loik did not like Valentino at first instance, taking his reserve for arrogance, but both soon found a way of understanding each other. The partnership of both attacking midfielders (mezzala in Italian) was based on the Loik's stubborn generosity and the Mazzola's rare talent. Soon, they became Italy's most coveted uprising young players.
He officially debuted for Torino on 20 September 1942, in the Coppa Italia against Anconitana Bianchi. The match ended 7–0 for Torino, with two goals by Mazzola. On the 4 October, he made his league debut for Torino. Both Mazzola and Loik played poorly because of their imprecision and their lack of understanding, and were considered responsible for the 1–0 defeat Torino suffered in Milan against Ambrosiana-Inter. Mazzola initially objected to the position he was played in for over two months, despite the team beginning to put together a series of victories. He scored his first league goal for Torino on 18 October in a 5–2 win over Juventus.
Mazzola made his debut for the national side on 5 April 1942, in a 4–0 friendly home win over Croatia. He scored his first international goal on 19 April, in a 4–0 friendly home win over Spain. Overall, Mazzola played 12 matches with the Italian national team between 1942 and 1949 and scored 4 goals, also serving as the side's captain between 1947 and 1949.