While in Congress, D'Alesandro strongly supported the Bergson Group, a "political action committee set up to challenge the Roosevelt Administration's policies on the Jewish refugee issue during the Holocaust, and later lobbied against British control of Palestine" despite his equally strong support for Roosevelt's other policies.

[2][5] On September 21, 1966, President Lyndon Baines Johnson's assistant Mildred Stegall requested a routine FBI name check on D'Alesandro.

[6] FBI records released on January 6, 2021 showed D'Alesandro had been the subject of a Special Inquiry investigation in March and April 1961, revealing numerous allegations of association with criminals in Baltimore.

In 1958, D'Alesandro ran for the United States Senate in a bid to defeat Republican incumbent J. Glenn Beall.

[9] In 2017, in an effort to counter D'Alesandro's daughter Nancy's efforts to remove statues of Confederate figures from the halls of Congress, conservative commentators noted that in 1948, D'Alesandro dedicated the Stonewall Jackson and Robert E. Lee Monument in his capacity as Mayor of Baltimore, along with the then-Governor of Maryland, William Preston Lane Jr.[10] His son, Thomas D'Alesandro III, who later served as Mayor of Baltimore from 1967 to 1971, said about his father "His whole life was politics.

[14] Two months after being present at Nancy's swearing in as a congresswoman, D'Alesandro died on August 23, 1987, in Baltimore, Maryland.