Roberts’ first husband was attorney Leo Panzirer, whom she divorced in 1952. Their only son was Jay (1940–1982), who had four children with his wife, Mimi. Jay died of heart failure at age 42. Leona was twice married to and divorced from her second husband, garment industry executive Joseph Lubin. After a brief period at a sewing factory, she joined a New York real estate firm, where she eventually became vice-president.

In 1968, while Roberts was working as a condominium broker, she met and began her involvement with the then-married real estate entrepreneur Harry Helmsley. Two years later, she joined one of Harry’s brokerage firms—Brown Harris Stevens—as a senior vice-president. At that time, she was already a millionaire in her own right. Harry divorced his wife of 33 years and married Roberts on April 8, 1972. The marriage may well have saved her career, as several of her tenants had sued her the year before for forcing them to buy condominiums. They won, and she was forced not only to compensate the tenants but to give them three-year leases. Her real estate license was also suspended, so she focused on running Harry’s growing hotel empire.

On March 31, 1982, Helmsley’s only child, Jay Panzirer, died of a heart attack resulting from arrhythmia. Her son’s widow, who lived in a property that Helmsley owned, received an eviction notice shortly after his funeral. Helmsley successfully sued her son’s estate for money and property that she claimed he had borrowed, and she was ultimately awarded $146,092.

Despite the Helmsleys’ net worth totalling over $1 billion, they were known for disputing payments to contractors and vendors. In 1983, the Helmsleys bought Dunnellen Hall, a 21-room mansion in Greenwich, Connecticut, to use as a weekend retreat. The property cost $11 million, but the Helmsleys wanted to make it even more luxurious. The work included a $1 million dance floor, a silver clock and a mahogany card table. The remodeling bills came to $8 million, which the Helmsleys were loath to pay. A group of contractors sued the Helmsleys for non-payment; the Helmsleys eventually paid off most of the debt owed to the contractors.

In 1985, during court proceedings in relation to the lawsuit, the contractors revealed that most of their work was being illegally billed to the Helmsleys’ hotels as business expenses. The contractors sent a stack of the falsified invoices to the New York Post to prove that the Helmsleys were trying to avoid tax liabilities. The resulting Post story led to a federal criminal investigation. Jeremiah McCarthy, the Helmsleys’ executive engineer, also alleged that Leona repeatedly demanded that he sign invoices to bill personal expenses to the Helmsley-Spear and, when McCarthy declined to do so, exploded with tyrannical outbursts, shouting, “You’re not my fucking partner! You’ll sign what I tell you to sign.” In 1988, then-U.S. Attorney Rudy Giuliani indicted the Helmsleys and two of their associates on several tax-related charges, as well as extortion.

In 1989, an unauthorized biography titled The Queen of Mean: The Unauthorized Biography of Leona Helmsley was published by Bantam Books ( ISBN 978-0553285581). The 1990 TV movie Leona Helmsley: The Queen of Mean starred Suzanne Pleshette as Leona and Lloyd Bridges as Harry. Pleshette was nominated for an Emmy Award and a Golden Globe Award for the portrayal.

Helmsley’s new lawyer, retained to appeal the judgment, was Alan Dershowitz. Following the appeal, which resulted in a reduced sentence, she was ordered to report to prison on tax day, April 15, 1992. She was released from custody on January 26, 1994, after serving nineteen months.

Helmsley’s later years were apparently spent in isolation, especially after Harry died in 1997. He left her his entire fortune, including the Helmsley hotels, the Helmsley Palace and the Empire State Building, estimated to be worth well in excess of $5 billion. Her few friends included Patrick Ward, Imelda Marcos, Rodrigo Handall, the Noriega family, and Kathy and Rick Hilton. A 2001 Chicago Sun-Times article depicted her as estranged from her grandchildren and with few friends, living alone in a lavish apartment with her dog. Helmsley was forced to give up control of her hotel empire, since most of her hotels had bars and New York does not allow convicted felons to hold alcohol licenses. She spent her final years at her penthouse atop the Park Lane Hotel.

In 2002, Helmsley was sued by Charles Bell, a former employee who alleged that he was discharged solely for being gay. A jury agreed and ordered Mrs. Helmsley to pay Bell $11,200,000 in damages. A judge subsequently reduced this amount to $554,000.

Although Helmsley had a reputation as the “Queen of Mean”, some considered her generous in her charitable contributions after her prison term. After the 9/11 attacks, Helmsley donated $5 million to help the families of New York City firefighters and police. Other contributions included $25 million to New York–Presbyterian Hospital for medical research in 2006 through a charitable trust fund, the donations eventually grew to $65 million to establish the Center for Advanced Digestive Care at the hospital in 2009.

Leona Helmsley died of congestive heart failure at the age of 87, on August 20, 2007, at Dunnellen Hall, her summer home in Greenwich, Connecticut. Cardiovascular disease ran in her family, claiming the lives of her father, son and a sister. After a week at the Frank E. Campbell Funeral Chapel, she was entombed next to Harry Helmsley in a mausoleum constructed for $1.4 million and set on ¾-acres in Sleepy Hollow Cemetery, Westchester County, New York. Among the few distinctive features of the mausoleum are three wall-embedded stained-glass windows, in the style of Louis Tiffany, showing the skyline of Manhattan. Leona Helmsley was known for not liking dirt and left $3 million for the 1,300 square foot Helmsley family mausoleum to be “washed or steam-cleaned at least once a year.”

Trouble lived in Florida with Carl Lekic, the general manager of the Helmsley Sandcastle Hotel, with several death threats having been received. Lekic, Trouble’s caretaker, stated that $2 million would pay for the dog’s maintenance for more than 10 years—the annual $100,000 for full-time security, $8,000 for grooming and $1,200 for food. Lekic was paid a $60,000 annual guardianship fee. Trouble died at age twelve in December 2010, at which time the remainder of the funds reverted to the Leona M. and Harry B. Helmsley Charitable Trust. Although Helmsley’s wishes were to have the dog interred with her in the mausoleum, New York state law prohibits interment of pets in human cemeteries and the dog was subsequently cremated.