The meeting with their Catalan neighbours at Camp Nou is the first of three games in eight days for the league leaders, with a trip to Las Palmas and a potentially crucial showdown with Atletico Madrid to come next week.
Portu opened the scoring for Girona in the 3rd minute only for Luis Suarez to equalize nearly directly from the kick off.
Los Blancos had a big day of their own, with their feared front three of Cristiano Ronaldo, Karim Benzema and Gareth Bale spearheading a 4-0 demolition of Alaves.
Messi took his competition-leading tally to 22 goals as Barcelona increased its lead of the Spanish league to 10 points before second-place Atletico Madrid visits Sevilla on Sunday.
Bagley returns, leads No. 5 Duke past Syracuse
Complemented by Carter Jr's 16 points and 10 rebounds, the play of Duke's bigs paved the way for their convincing victory. Bagley jumped toward the rim, catching Allen's pass over a Syracuse defender and throwing it down for a two-handed dunk.
This Barcelona side beat the record set by Pep Guardiola's Barcelona side of 2011 which went 31 matches unbeaten in La Liga.
Barca's victory against Girona sees them stay top of the table, with 20 wins and five draws from 25 games.
Girona's joy was short-lived as Suarez restored parity with a fine finish after latching onto a pass from Messi in the fifth minute.
Asked after the game about Messi's free kick, Barca coach Ernesto Valverde said in a news conference: "It's hard to get used to these things".
Suarez crashed a shot against a post early in the second half and Bono's save denied Messi his hat-trick before Coutinho showcased his talents with a superb curling effort to put Barcelona 5-1 ahead in the 66th minute.
Valverde started Barcelona's two record signings for the first time since having them both available, with Coutinho and Ousmane Dembele lining up alongside Messi and Suarez. Cristian "Portu" Portuguese struck early for Girona when he caught Samuel Umtiti being far too complacent when he raced in from behind to reach a ball near Barcelona's box.