The two envoys escaped unharmed when bullets hit their car in the Shiite-dominated Awamiya area three years ago, police said at the time.
Awamiya, on the Gulf Coast near Dammam, has been a centre of unrest among the minority Shiite community since protests began there in 2011 and developed into a call for equality.
A trial began on Sunday in Riyadh for the suspect, who was not named but could face the death penalty, Okaz newspaper reported.
Almost a year after the shooting the interior ministry said it had arrested a suspect, Salem bin Abdullah bin Hussein, who was wanted for a number of violent crimes.
Okaz reported that the man on trial before a court specialising in "terrorist" cases is accused of several offences.
These include attacking a diplomatic vehicle, attempting to kill police, participating in demonstrations, inciting sedition and causing sectarian strife, the newspaper said.
The Germans' car was hit by fire from an automatic weapon which caused the vehicle to burn, it said.
Okaz said the accused asked the court for one month to prepare his defence.
German media reports after the shooting said the two Germans worked for their country's BND foreign intelligence service, something Berlin's foreign ministry declined to comment directly on at the time.
Awamiya was the home of Shiite cleric Nimr al-Nimr, who was convicted of terrorism and executed one year ago.
Nimr was a driving force behind protests by Shiite residents that began in 2011 and developed into a call for equality.
Most of Saudi Arabia's Shiites live in the east and have long complained of marginalisation in the Sunni-dominated kingdom.
Data from activists late last year showed 25 Shiites were on death row allegedly related to incidents since 2012 in Qatif, the Shiite-dominated area that includes Awamiya.