Younes A. was found guilty of petty theft in a Cologne court on Wednesday, local newspaper Express reports.
The 23-year-old stole a mobile phone from a young woman as she was taking photos of Cologne's famous cathedral.
The accused used the chaos at the scene, where mass sexual assaults were taking place, to rob the woman and then tried to run away with her phone, the judge ruled.
But the woman was able to catch him and hand him in to police who arrested him.
The young Moroccan has been in custody since the time of his arrest.
He has applied for asylum but did not name the reasons for his application in court. Through his defence lawyer he admitted to the crime but said he had nothing to do with the sexual assaults which happened on the same evening.
The victim of the crime described how, after travelling from southern Germany for the Cologne celebrations, she was groped almost as soon as she disembarked at Cologne train station.
Two other men are also appearing in court on Wednesday charged with robbery in the first criminal cases brought over events in Cologne on New Year's Eve.
The two men are alleged to have stolen a camera from a man.
The trials will be the first step towards achieving justice for more than 1,000 people who reported crimes in and around the western cathedral city's main train station on New Year's Eve.
But none of the men is charged with sexual assault – the key feature of the night which made it a lightning rod for fears about migration all over Germany, Europe and the world.
Women reported being surrounded, groped and threatened by large groups of men of north African and Middle Eastern appearance.
Among the more than 1,000 crime reports dealing with that night, more than 430 deal with sexual assault – up to and including rape.
The three men on trial in Cologne are from Morocco and Tunisia and are aged between 18 and 23 years.
All three have been in investigative custody since New Year's Eve.