Ernesto Valverde's side were crowned champions after a 4-2 win at Deportivo La Coruna in late April, but will not be finishing La Liga unbeaten after losing 5-4 away to Levante last weekend.
Barca are now home to Real Sociedad in their final league game, Iniesta's farewell before moving to Asia this summer, and here Goal takes a look at everything you need to know ahead of Sunday's clash at Camp Nou...
Sergi Samper is sidelined with a long-term injury, while Thomas Vermaelen is out after limping off against Levante last weekend. Samuel Umtiti is doubtful with a minor knee problem.
Sergi Roberto was hit with a four-match ban for lashing out at Marcelo in the Clasico and will therefore not appear again in La Liga this season.
Barcelona potential starting line-up
Valverde is set to field a strong side for Barcelona's last game of the season as Camp Nou bids a fond farewell to Iniesta on Sunday.
The Spain midfielder will start his final game for Barca before leaving the Catalan club this summer and that means Philippe Coutinho is set to play on the right.
In defence, Yerry Mina could feature despite his poor performance against Levante because Umtiti is doubtful and Vermaelen sidelined.
Nelson Semedo will start at right-back in place of the suspended Sergi Roberto. Luis Suarez and Lionel Messi are expected to be included from the outset in attack.
Real Sociedad team news
Real Sociedad are 10th in La Liga after last weekend's win over Leganes, but defeat at Camp Nou on Sunday could see the Basque side finish in the bottom half after what has been an inconsistent season.
Captain Xabi Prieto is retiring at the end of the season and the midfielder is expected to come off the bench at Camp Nou.
Defender Carlos Martinez is also hanging up his boots this summer, but he is doubtful for Sunday's game. Centre-back Hector Moreno and striker Imanol Agirretxe are both sidelined.
TV channel & kick-off time
Barcelona versus Real Sociedad kicks off at 8:45pm local time on Sunday and will be broadcast live in the UK (United Kingdom) on Sky Sports Football and Sky Sports Main Event from 7:40pm BST.
In the United States, the game can be watched live on television on beIN SPORTS and kicks off at 2:45pm ET.
Best Opta match facts
No home team has defeated Real Sociedad more times in La Liga than Barcelona, the Catalans winning 60 of the 70 games they have hosted against the Basques.
Barca are unbeaten in 35 consecutive games at Camp Nou in La Liga (won 29, drawn six), their best unbeaten home streak at home in the competition since November 1993 (won 34, drawn six).
Willian Jose has been involved in four goals in his four league appearances against Barca (three goals and one assist).
Lionel Messi has scored 10 goals in his nine games versus Real Sociedad at Camp Nou in all competitions.
This game will be a farewell for Iniesta and Xavi Prieto in La Liga after 441 and 375 league games played, respectively.