On 2 May 2015, Vidal scored the only goal of a 1–0 win at Sampdoria, confirming La Vecchia Signora as Serie A champions for the fourth consecutive season. On 20 May, he appeared in Juventus' 2–1 win over Lazio in the 2015 Coppa Italia final, as Juventus captured a domestic double and their tenth Coppa Italia title. On 6 June 2015, Vidal started for Juventus in the 2015 Champions League final as La Vecchia Signora was defeated 3–1 by Barcelona at Berlin's Olympiastadion.
On 15 July 2015, Vidal was named to the ten-man shortlist for the 2015 UEFA Best Player in Europe Award; on 12 August, it was announced that he placed eighth in the 2015 UEFA Best Player in Europe Award.
On 28 July 2015, Vidal returned to the Bundesliga, joining Bayern Munich on a four-year deal for a fee of €37 million plus up to €3 million in bonuses. Vidal made his debut for Bayern four days later in the 2015 DFL-Supercup against VfL Wolfsburg, as a 74th-minute substitute for Thiago. The match finished in a 1–1 draw; Bayern lost in a shootout where Vidal scored. Vidal scored his first goal from the penalty spot against FC Nöttingen in the fifth minute of Bayern's first round DFB-Pokal match. On 19 September, he scored his first league goal for Bayern in a 3–0 away victory over SV Darmstadt 98. On 26 November, Vidal was nominated for the 2015 UEFA Team of the Year. He scored two goals in both first leg and second leg of the Champions League quarter-final tie against S.L. Benfica which helped his side to go through to the semi-final.
On 11 June 2015, five days after appearing the 2015 Champions League final for Juventus, Vidal scored the opening goal of the 2015 Copa América from the penalty spot in Chile's 2–0 win over Ecuador at the Estadio Nacional in Santiago, having won the penalty himself when fouled by Miller Bolaños. In the team's next group fixture, Vidal scored twice – a header from a corner and another self-earned penalty – and set up another as the hosts drew 3–3 with Mexico on 15 June. In the final group game, a 5–0 win against Bolivia three days after his drunk driving charge, Vidal and Alexis Sánchez were rested by being substituted at half-time. On 4 July, in the 2015 Copa América final, Vidal scored from a penalty in Chile's 4–1 shoot-out victory over Argentina; in the final, he was voted Man of the Match, and was later named to the 2015 Copa América Team of the Tournament for his performances.
On 16 June 2015, during the 2015 Copa América, Vidal suffered minor injuries when he crashed his Ferrari while under the influence of alcohol in Santiago. He left the hospital in a police car and was summoned to court to face charges for drunk driving. On 8 July 2015, Vidal was given a two-year driving ban, however he was allowed to continue playing in the Copa América that year. His cousin, Gonzalo Vásquez, is a former footballer who is now an engineer.