The 2012 edition marked the 60th running of the Sebring 12 Hours and the debut race of the newly launched FIA World Endurance Championship, which replaced the earlier Le Mans Series structure. The race was also the one and only event in which the ALMS and WEC fields competed together, creating an unusually complex grid of nine separate classes: LMP1, LMP2, LMGTE Pro and LMGTE Am under WEC rules, alongside P1, P2, PC, GT and GTC under ALMS regulations. The FIA track homologation set a 64-car entry limit; 63 cars ultimately started.
Defending champions Peugeot did not return, having withdrawn from endurance racing. Audi Sport Team Joest fielded three R18 TDI cars as the only factory LMP1 manufacturer, and the Audi R18 TDI driven by Marcel Fässler, André Lotterer and Benoît Tréluyer started from pole position after Lotterer set the fastest qualifying lap.
The race started at 10:30 a.m. local time. Allan McNish passed Lotterer on the opening lap to hand the lead to the sister number 2 Audi driven by Rinaldo Capello, Tom Kristensen and McNish. That car led all but 66 laps across the twelve hours. The race featured eleven full course cautions, a new record for Sebring, as incidents across the sprawling multi-class field repeatedly interrupted the action.
Audi's march to victory was not entirely smooth. Fässler's number 1 car suffered a recurring gear selection issue traced to an electric motor driving the gearbox's selection mechanism, causing multiple pit stops. In the final hour, Simon Pagenaud's number 6 Muscle Milk HPD LMP1 car retired due to a fuel valve failure. These developments did not threaten the lead Audi, which completed 325 laps to finish four laps ahead of the sister number 3 car of Timo Bernhard, Romain Dumas and Loïc Duval. The R18 TDI's one-two result was described as the model's final race appearance.
Capello, Kristensen and McNish's victory was a record-laden result: it was Kristensen's sixth Sebring victory, Capello's fifth, McNish's fourth, and Audi's tenth overall win at Sebring. In the WEC LMP2 class, Ryan Dalziel, Enzo Potolicchio and Stéphane Sarrazin of Starworks Motorsport won in an HPD ARX-03b, finishing third overall after a two-hour battle with the Level 5 Motorsports HPD driven by João Barbosa, Christophe Bouchut and Scott Tucker, who took the ALMS P2 class.
In the GT category, Joey Hand, Dirk Müller and Jonathan Summerton of BMW Team RLL overcame a final-lap collision — when their sister AF Corse Ferrari bumped Hand in an attempt to unlap — to take the ALMS GT class victory over Corvette Racing. The bump spun Hand off the track; he regained control and overtook the AF Corse Ferrari of Olivier Beretta. The AF Corse number 51 Ferrari was subsequently disqualified for unsportsmanlike conduct, and Bruni was fined $15,000 by race officials. Beretta's number 71 AF Corse Ferrari won the WEC LMGTE Pro class.
The LMGTE Am class produced a dramatic finish when Pedro Lamy's number 50 Larbre Compétition Corvette lost its driveshaft with 16 minutes remaining while leading, handing the class win to Team Felbermayr-Proton's Porsche 997 GT3-RSR of Christian Ried, Gianluca Roda and Paolo Ruberti. Ruberti drove the final stint without power steering. Alex Job Racing claimed their eighth Sebring category win in GTC, with Townsend Bell, Dion von Moltke and Bill Sweedler's Porsche one lap ahead of the sister AJR entry.
The 2012 12 Hours of Sebring was a logistical and sporting achievement in combining two major endurance series at a single event, but the complexity of nine classes racing under different championship regulations drew criticism. ALMS president Scott Atherton praised the cooperation between the organisations, but commentators noted that the overlapping class structures created confusion for spectators and competitors alike. The WEC did not return to Sebring, with the series' American presence later established at the Circuit of the Americas; it was not until the 2019 1000 Miles of Sebring that the FIA series returned to the Florida venue. The 2012 edition nonetheless stands as a significant moment in the consolidation of international sports car racing, preceding the eventual merger of the ALMS into what became the IMSA WeatherTech SportsCar Championship in 2014.