A big-rig was in the right lane moving slowly as it began its ascent up the Altamont Pass at about 12:30 p.m. when another big-rig rear-ended it, California Highway Patrol Officer Steve Creel said.
A third big-rig then came along and slammed into the back of the second big-rig.
The driver of the first truck was not injured, but the other two drivers were both transported to hospitals. One was airlifted to Eden Medical Center in Castro Valley and the other was taken by ground ambulance to San Joaquin General Hospital in French Camp, Creel said.
Ten to 15 gallons of diesel fuel was spilled on the roadway.
The two right lanes of the highway remained closed as crews cleared the big-rigs and cleaned up the fuel.
CHP Officer Aaron Quistad said all lanes were open just before 6 p.m. Traffic in the area remained slow around 7:10 p.m., he said.