The 28-year-old footballer entered the guilty pleas at Bradford Crown Court this morning on what was the first day of his trial for four allegations.
He admitted meeting a child following sexual grooming and one charge of sexual activity with a child.
Johnson, of Castle Eden, County Durham, still stands accused of two counts of sexual activity with a child, which he has denied.
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A jury of 12 people has been sworn in, and instructed by Judge Jonathan Rose that they will begin to hear the case of the England International on Friday.
Johnson, who has 12 caps for his country, appeared in the dock wearing a black suit and white shirt and was flanked by a female prison officer.
He listened carefully as the proceedings got under way as six men and six women were selected to sit on the jury.
In his directions, Judge Jonathan Rose told the jurors that Johnson had already pleaded guilty to two charges.
Minutes earlier, Johnson had stood in the dock to admit his guilt on the grooming charge and a further charge of sexual activity which involved kissing and touching the youngster’s body.
He added that they may read about the case in the press.
He told the jurors: “Mr Johnson, as you will hear, is a professional footballer for Sunderland Football Club.”
They were instructed that they try the defendant on only the evidence they hear in court.
Judge Rose added: “You may see reference to this in the press but it’s the evidence in court that you will gather.
“This defendant has already pleaded guilty to two offences, you will hear more about them in detail when Miss Blackwell opens the case to you on Friday.”
He said they must come to a decision on the remaining two charges.
“It will be for you and only you to determine if he is guilty or not guilty.”
The defendant, from Castle Eden, County Durham, had his case moved from Durham.
Kate Blackwell, QC for the prosecution, said that the alleged incidents had taken place in County Durham.
Johnson is being represented by Mr Orlando Pownall QC. Twelve journalists were allowed into the hearing which saw a further 18 people including the footballer’s girlfriend, Stacey Flounders, who was accompanied by another woman, sat in the public gallery.
Born in Sunderland, Johnson began his career at Middlesbrough before moving to Manchester City and then to Sunderland for £10 million in 2012.
Legal argument will now take place before the case is scheduled to be formally opened on Friday.
Video footage c/o BBC.