However, Brueckner will remain in prison another year because he is still serving a seven-year sentence for rape in a different case, German news agency dpa reported.
Brueckner had been on trial since February over offences he is alleged to have committed in Portugal between 2000 and 2017.
Defence lawyers had pointed to what they labeled a lack of evidence and witnesses who weren’t credible, and suggested he might not have been charged if he hadn’t also been a suspect in the McCann case.
Prosecutors had argued he should be given a 15-year prison sentence and kept in preventive detention once he has served it.
“The evidence we had was not enough to convict the defendant,” presiding judge Uta Engemann said, according to dpa, adding that “we were dealing with unreliable witnesses, some of whom deliberately lied to the court”.
Engemann argued that witnesses had been influenced in their statements by the media’s reporting on Brueckner, who she said had been “stylised as a sex monster and child murderer”.
The verdict can be appealed, dpa reported.
Brueckner has not been charged in the McCann case, in which he is under investigation on suspicion of murder.
He spent many years in Portugal, including in the resort of Praia da Luz around the time of Madeleine’s disappearance there in 2007. He has denied any involvement in her disappearance.
He is currently serving a seven-year prison sentence after being convicted in 2019 by the Braunschweig court for the rape of a 72-year-old American woman in Portugal in 2005.
The Braunschweig state court has jurisdiction because Brueckner had his last German residence in that city in Lower Saxony.