Under British divorce law, the decree nisi is essentially a preliminary divorce. The McCartneys now must wait six weeks and one day to receive a decree absolute, which ends the marriage completely.
Justice Hugh Bennett ended the couple's marriage on grounds that they have been separated for two years. Neither McCartney, 65, nor Mills, 40, appeared in court.
The decree paves the way for Mills to receive her $48.6 million divorce settlement, which was granted in March.
McCartney married Mills in 2002, four years after the death of his first wife, Linda. The pair separated in May 2006 and McCartney filed for divorce in July of that year. They have a four-year-old daughter Beatrice.