As a trusts and estates lawyer, Roy A. Hammer oversaw mountains of old money in Boston for decades, and he managed the business affairs of one of the nation’s wealthiest families with a tight lip, a wry sense of humor, and a reputation for the highest ethics and integrity, his family and colleagues said.

While spending his entire law career at Hemenway & Barnes, Mr. Hammer was the trustee for the Bancroft family during the last decades of the family’s legendary ownership of The Wall Street Journal and its control of Dow Jones & Co.

“He was the best possible person to have in your corner,’’ his cousin Amy S. Langer of New York said. “He had a brilliant mind and a strong moral compass. He really was someone very special.’’

Mr. Hammer, a former chairman of the Civil Liberties Union of Massachusetts and a former member of the American Bar Association’s board of governors, died April 26 in Spaulding Nursing and Therapy Center in the North End after a period of declining health. He was 81 and lived in Boston.

“Roy gave us decades of selfless, consistent, and brilliant service to our profession. Day after day, he showed the importance of caring, of listening, and of always thinking about who might be harmed by a decision, who could be helped, and how we can make our system of justice serve everyone,’’ said Lauren Stiller Rikleen, an attorney who served with Mr. Hammer on the American Bar Association’s section of civil rights and social justice.

“His greatest legacy, however, is that he did all this with kindness, decency, and a humbleness that is increasingly rare,’’ she said.

Before curbside recycling became widespread, Mr. Hammer could be seen riding the Red Line carrying soda cans collected from the office. He took them home to recycle when he lived in Cambridge, colleagues said.

Lanky and unassuming, he consistently donated blood and extolled members of his firm to join him when the American Red Cross Bloodmobile came around.

By 1997, he oversaw more than 170 private trusts, according to a profile in American Lawyer that called him “discreet and precise’’ and “an archetypal trusts and estates lawyer.’’ His firm earned more than $2 million in 1996 from managing the Bancroft trusts, according to American Lawyer.

In the mid-1990s, it fell to Mr. Hammer to manage a public rebellion by some of the younger Bancrofts against the structure of the family trusts. “Disgruntled heiress leads revolt at Dow Jones,’’ was a February 1997 Fortune magazine headline.

The younger generation voiced concern that the older generation benefited from rising Dow Jones dividends while younger family members had to cope with languishing stock prices reducing their inheritance.

Those at Hemenway & Barnes endured claims from a Bancroft heir that as trustees, they favored the older Bancrofts in order to increase the firm’s income. Mr. Hammer found himself in the glare of an unfamiliar spotlight as he and his partners insisted that the firm’s compensation arrangement did not affect the advice they offered.

The Bancroft family squabble eventually cooled. In 2002, Jane Bancroft Cook — who was the largest family shareholder at Dow Jones, and who became a member of the board in 1949 — died at age 90.

In 2006, Mr. Hammer retired from full-time work at Hemenway & Barnes and became of counsel. The next year, the Bancroft legacy of operating The Wall Street Journal as a public trust for more than a century ended. The company acceded to Rupert Murdoch’s News Corp. $5 billion takeover bid.

“There was no question Roy supported that as the right choice, but it was certainly also a painful and difficult one. It was the right thing to do in terms of the time and the terms of the sale, but no one likes to see that kind of era come to an end,’’ said Michael Puzo, senior partner at Hemenway & Barnes, who worked with Mr. Hammer for 39 years.

Born in New York City, Mr. Hammer grew up in the Bronx with his older sister, Maxine. His family lived above a pharmacy run by his grandfather, who had emigrated from Poland as a teenager.

Mr. Hammer was only 13 when his father, Joseph, who was a lawyer, and his mother, the former Beatrice Kopald, both died within a year of each other, according to his family.

His aunt Teresa became his legal guardian. She was one of a handful of women who graduated from the Fordham University School of Law in the late 1920s.

Mr. Hammer went to high school at Loomis Chaffee, a boarding school in Windsor, Conn. A week after his graduation from Yale University in 1956, he married his longtime love, Sylvia, whom he had first met at family gatherings when they were children.

Having lost his parents as a teenager, Mr. Hammer seemed to hunger for a family of his own, his wife said. “He wanted family experiences,’’ she said. “He has always been, above and beyond everything else, a family man. He was very grateful to have a family.’’

Mr. Hammer served in the Army and graduated with a master’s in American literature from Columbia University in the 1950s. He initially planned a career in academia, but decided to study law. He graduated from Harvard Law School in 1960 and was hired at Hemenway & Barnes, where he had a summer job.

In addition to his wife, Mr. Hammer leaves his daughters, Julie of Providence and Beth Isa of Lexington; and four grandchildren.

A private funeral was held, and a remembrance gathering will take place at 11 a.m. June 3 in the Colonnade Hotel in Boston.

As chairman of the Civil Liberties Union of Massachusetts in the early 1970s, Mr. Hammer presided during unprecedented growth. In less than two years, the organization brought more cases to court than it had handled in the previous 47 years, he told the Globe. The cases were mostly violations of First Amendment rights, including a high school student who was sentenced to carry the US flag for 3 miles after she burned one.

Mr. Hammer also battled what he called “legislative hysteria’’ in response to antiwar protesters. In a May 1970 letter to the editor that the Globe published, he argued that proposed state laws would stifle legitimate protests. “We must defend those wise restraints which make men free, but we must be equally vigorous in opposing unwise restraints which erode our political rights,’’ Mr. Hammer wrote.

“When Roy spoke, people listened,’’ said John Roberts, who began his long tenure as director of Civil Liberties Union of Massachusetts under Mr. Hammer. The organization later changed its name to the American Civil Liberties Union of Massachusetts.

“Roy was just solid. He was a rock for the organization and certainly for me,’’ said Roberts, who was executive director for 32 years.

Mr. Hammer, a former Massachusetts Bar Association president, also was a member of the Handel and Haydn Society board of governors and a trustee of the Longy School of Music.

In 2011, the American Bar Association gave him the Robert F. Drinan Award for Distinguished Service, honoring his leadership in protecting and advancing human rights, civil liberties, and social justice.

“He had a beautiful mind and a beautiful soul and I miss him very much,’’ his law partner Puzo said.

J.M. Lawrence can be reached at jmlawrence@me.com.