On 28 September, Barcelona defeated Borussia Mönchengladbach 1–2 with goals from Turan and Gerard Piqué, turning around a 1–0 first-half deficit to Barça top of Group C. On 24 September, Barcelona won 0–5 over Sporting de Gijón through two goals from Neymar and one each from Suárez, Turan and Rafinha.
On 21 September, Barcelona drew against Atlético Madrid 1–1 Ivan Rakitić gave Barça the lead before half-time, but Atlético battled back to draw level in the second half after Messi was substituted out due to injury. Barcelona won 1–5 with two goals from Messi and one each from Luis Suárez, Neymar and Rafinha. On 17 September, Barcelona faced for the first time recently promoted Leganés at the Estadio Municipal de Butarque. Messi notched his first hat-trick of the season, while Neymar provided four assists and a free-kick goal. On 13 September, Barcelona defeated Celtic 7–0 in the opening match of Group C in the Champions League. On 10 September, in the match against Deportivo Alavés, Barcelona suffered a 1–2 defeat.
On 30 August, the club completed the last transfer of Paco Alcácer from Valencia. On 28 August, Barcelona defeated Athletic Bilbao 0–1 with a goal from Rakitić and Luis Enrique wins his 100th match as Barça manager, Ter Stegen made most goalkeeper passes in one single match in LaLiga. Several hours later, both teams were drawn into Group C of the Champions League draw, alongside Borussia Mönchengladbach and Celtic.
On 25 August, the club completed the transfer of 27-year-old goalkeeper Jasper Cillessen from Ajax on a five-year contract, with goalkeeper Claudio Bravo then joining Manchester City after two years with Barça. On 20 August, Barcelona defeated Real Betis 6–2 in their first Liga match, with a hat-trick from Luis Suárez, two goals from Messi and one from Arda Turan. On 18 August, Barcelona beat Sevilla with 3–0 (5–0 aggregate) and won their 12th Supercopa de España. On 14 August, Barcelona won the first official match in the 2016 Supercopa de España against Sevilla with a 0–2 away score. On 10 August, the 2016 Joan Gamper Trophy was played against Italian club Sampdoria, finishing 3–2 with a goal from Luis Suárez and two from Lionel Messi. On 8 August, the club loaned Thomas Vermaelen to Italian club Roma with an option to buy. On 6 August, Barcelona were soundly defeated by Liverpool 4–0 at Wembley Stadium in London. On 3 August, Barcelona defeated English Premier League champions Leicester City 4–2 in Stockholm with goals from Munir (2), Luis Suárez and Barcelona B player Rafa Mújica. On 1 August, the club cancelled the contracts of Alex Song and Martín Montoya. On 30 July, Barcelona won their first pre-season match against Scottish champions Celtic with a 1–3 score in Dublin as part of the 2016 International Champions Cup. ĭuring the press conference of Gomes' presentation, the club announced midfielder Javier Mascherano's contract was extended until 30 June 2019. On 21 July, Barcelona and Valencia reached an agreement for the transfer of Portuguese international midfielder André Gomes. On 19 July, Barcelona and Qatar Airways extended sponsorship agreement for one year more. On 19 July, Barcelona and Munir El Haddadi also negotiated a three-year contract extension lasting until 30 June 2019. On 19 July, Barcelona and Sergi Samper negotiated a three-year contract extension lasting until 30 June 2019, including promotion to the first team. On 14 July, the two transfers were completed. On 12 July, the club announced the transfers of 22-year-old French international defender Samuel Umtiti from Lyon and Lucas Digne from Paris Saint-Germain for the next five seasons, respectively. On 4 July, the club completed the transfer of Denis Suárez. On 1 July, Barcelona and Neymar negotiated a five-year contract extension lasting until 30 June 2021. On 5 June, the club announced that Denis Suárez will be forming part of the first team for this season. On 3 June, Barcelona announced that German club Borussia Dortmund have informed them of their desire to activate the buy-out clause for Marc Bartra. On 2 June, Barcelona announced that Dani Alves would be departing the club after eight seasons. On 1 June, the club announced that Sandro Ramírez's contract would be rescinded.