Alec Wallbank, 31, from Pontypridd, was found not guilty of two charges at Cardiff Crown Court in January.
Prosecutors have now said they are not proceeding with four more allegations, and not guilty verdicts have been recorded.
It was claimed Mr Wallbank had sex with a woman discharged from Cardiff's Whitchurch Hospital.
But his trial was halted when Judge Thomas Crowther QC told the jury to find the carer not guilty of two counts of engaging in sexual activity with a patient.
Mr Wallbank had always denied all the allegations against him.
Prosecutors said on Wednesday that they would not be offering any evidence in the outstanding four charges being faced by Mr Wallbank.
A mental health ward worker accused of sexual activity with a female patient has been cleared of all charges.