Mouloud Tahari, 20, from Sparkhill, Birmingham, appeared at the Old Bailey in March charged with funding terrorism overseas.
But West Midlands Police said he would no longer stand trial.
His mother, Gerri Tahari, is due to appear before a jury on September 8 charged with the same offence.
A spokesman for the force said: "The case against Mouloud Tahari was discontinued after consultation with the Crown Prosecution Service.
"It was decided there was insufficient evidence to for a realistic prospect of conviction."
A man accused of a terrorism offence relating to the civil war in Syria has been told he will face no further action because of a lack of evidence.