"The traditional way, if you look at President Obama and other presidents, most of them didn't make calls," Trump said during a Rose Garden press conference, flanked by Senate Majority Leader Mitch McConnell.
"A lot of them didn't make calls. I like to call when it's appropriate, when I think I am able to do it," the president added.
Several minutes later Trump was pressed on his claim by a journalist, particularly about Obama.
"I don't know if he did. No," Trump said. "I was told that he didn't often, and a lot of presidents don't. They write letters ... I do a combination of both."
"President Obama, I think, probably did sometimes, and maybe sometimes he didn't. I don't know. That's what I was told," Trump added.
Trump: 'I wrote to families of fallen, they're going out either today or tomorrow'
Trump spoke about the letter-writing issue when he was asked why he remained mum for 12 days following the deaths of four American soldiers during an ambush in Niger.
It was the deadliest attack on American forces since Trump took office in later January of this year.
Trump, who went golfing this past weekend, said he was going to call the families "when it's appropriate," and that he'd already written them leaders which will be mailed "today (Monday) or tomorrow."
Obama's former aides were quick to lash back at Trump's claims. Former Obama Deputy Chief of Staff Alyssa Mastromonaco tweeted Trump was a "deranged animal," adding he's a "f***ing liar".
"To say President Obama (or past presidents) didn't call the family members of soldiers KIA – he's a deranged animal," Mastromonaco accused.
Delilia O'Malley, an American woman whose brother was killed during George W. Bush's administration was also infuriated by Trump's comments. "When my brother was killed, Pres Bush listened while I screamed at him & then held me as I sobbed, you fat f***ing liar," she tweeted in a post that received more than 155,000 retweets.
Freddy Ford, former spokesman for President George W. Bush, said Bush wrote to "all the families of the fallen" during his term in office and called or met "hundreds if not thousands" of the relatives of fallen soldiers.
During Bush's eight years in the White House, more than 4,000 American soldiers were killed.
Obama also called the families of fallen soldiers and wounded army veterans and even met some of them, as documented by the White House itself.
Former official White House photographer Pete Souza published a photo of Obama comforting the parents of killed American soldier Jared Monti in 2009. On his Instagram account, Souza wrote Obama visited "hundreds" of families of wounded or killed soldiers.
Obama also arrived to the Dover Air Force Base in Delaware on at least two occasions to greet coffins of soldiers killed in actions before they were sent to their families. In 2009, for instance, he saluted as 19 killed American soldiers returned to the US in coffins and met 250 relatives of 30 soldiers killed in Afghanistan when their plane was shot down for more than an hour.
The Associated Press contributed to this report.