The 28-year-old former Sunderland winger admitted kissing the girl in his car and grooming her with hundreds of social media messages.
After he was found guilty of a more serious charge of sexual activity with the teenager, a judge told him he should expect to receive a substantial prison sentence.
Johnson was given bail at Bradford Crown Court by Judge Jonathan Rose, who warned him: "You must understand that when you return here at the end of March you will receive a substantial prison sentence."
Justifying giving him bail on 2 March, the judge said: "You can say goodbye to your daughter. A prison sentence will mean you will not see her for some time."
The judge said his preliminary view was that the offences fall into the category of a five-year prison sentence with a possible range of four to 10 years.
Johnson was found not guilty of a third charge of sexual activity with a child, relating to the same girl.
All the charges relate to an incident in Johnson's Range Rover when he met up with the girl in County Durham on 30 January last year.
In a statement read by a police officer outside court, Johnson's teenage victim, who cannot be identified, said: "I felt used and let down by him.
"It's been the hardest year of my life and I've had to face so much abuse after he claimed his innocence."
She added: "There have been times when I've tried not to show people how upset I am, but sometimes it hasn't been possible and I'd just cry. I've felt so broken."
The jury heard how Johnson, who played for England 12 times, began exchanging hundreds of messages with the girl on social media at New Year 2015.
He eventually agreed to meet her to sign football shirts but it was during a second meeting, after he inquired about a 'thank you kiss', that the sexual activity happened.
After Johnson's trial, a row erupted over just how much Sunderland AFC knew about what their player had done when they let him play on before finally sacking him earlier this year after his guilty pleas.
Earlier this week the club said it was 'so very sorry' for letting down their 15-year-old fan after chief executive Margaret Byrne resigned.
Ms Byrne admitted 'a serious error of judgment' in advising the board that the star winger could carry on playing after he was initially suspended last March.
Johnson, a $19.17 million signing, helped the Wearside team to narrowly avoid relegation from the Premier League last year.
The player has a one-year-old daughter with Stacey Flounders, who supported him during the court case but who told the jury they were now just friends.
Johnson, of Castle Eden, County Durham, was bailed on condition he lived at his home address and did not contact witnesses.
The player was also ordered to observe a 7pm to 7am curfew.