Napa County sheriff's Capt. Tracey Stuart identified the crash victim as 42-year-old Sgt. David Robert Fernandez.
Fernandez and Michael Manalo, 31, of Fairfield, were riding their Yamaha motorcycles east on state Highway 128 east of Wragg Canyon Road when the crash happened around 12:45 p.m., CHP Officer Jaret Paulson said.
Both motorcyclists were passing traffic as they approached a 1997 Chevrolet van that was being driven east on the highway by Austin Meade, 28, of Oakland, Paulson said.
Meade turned left toward the road's north shoulder in front of the bikers and the motorcycles broadsided the van, Paulson said.
Fernandez was pronounced dead at the scene at 1:40 p.m. Stuart said. Manalo suffered moderate injuries and was taken by ambulance to the Queen of the Valley Medical Center, Paulson said.
Meade was not injured and was booked into Napa County Jail on suspicion of DUI, Paulson said.