During this time J. Seward Johnson' engaged in extramarital affairs with Piasecka Johnson. In 1971, they married with none of Johnson's children in attendance. According to trial witnesses brought to court by J. S. Johnson's children during the proceedings concerning his will, Piasecka Johnson "often physically and emotionally abused her husband". Piasecka Johnson said she was a devoted wife for 12 years of marriage.
She was the primary beneficiary of his will and received the bulk of her husband's fortune of $400 million after he died in 1983 ($983 million as of 2017). Excluded from their father's will, Seward Johnson's six children sued on grounds that their Father wasn't mentally competent at the time he signed the will. The case went to trial but was settled prior to return of a verdict, and the children were granted about 12% of the fortune, leaving Piasecka Johnson in control of the majority of the estate.
Paintings from Piasecka Johnson's art collection were displayed in Monaco's Museum of the Chapel of Visitation from 1995 to 2014. Her collection was removed from the chapel in May 2014 in preparation for its eventual sale at Christie's auction house in July 2014.