Despite - or because of - her military background, she has opposed U.S. involvement in Syria and faced criticism for visiting that country and meeting President Bashar al-Assad.
She said she does not regret the trip and considers it important to meet with adversaries if "you are serious about pursuing peace".
More recently, Gabbard stirred controversy among fellow Democrats when she issued a statement accusing some of them of "religious bigotry" for questioning whether a judicial nominee's membership in a Catholic fraternal organization would affect his ability to apply the law.
The Hawaii Democrat said there were "a lot of reasons" behind her decision to run and named some of the top issues that would be on her campaign platform, including health care, criminal justice reform and climate change.
Her endorsement came in dramatic fashion, with her resigning as a vice chairwoman of the Democratic National Committee (DNC) to express her support.
Kamala Harris, 54, who is of Indian and African-Jamaican descent and is identified as a member of the Christian Baptist sect, is expected to announce her candidature for the Democratic Party nomination next week, according to several news reports quoting sources close to her.
The US senator Elizabeth Warren, of MA, on 31 December announced she had formed an exploratory committee for a presidential run in what is expected to be a crowded Democratic primary field before the November 2020 presidential election.
Gabbard has earned her right to be critical of those conflicts.
Gabbard, 37, is widely known for her unorthodox positions within the Democratic caucus.
Her father Mike Gabbard, a Hawaii State Senator, told the local Hawaii News Now: "I didn't know she had made a final decision".
"Assad apologist" seems to be the Tulsi equivalent of "Putin puppet", judging from the early tweets, though she was accused of being one of those too. Elizabeth Warren (D-Mass.), Sen.
Gabbard enters a 2020 Democrat primary field which will likely go into double-digits.
Gabbard moved to Hawaii when she was two and embraced Hinduism as a teenager and is well-versed in the scriptures, PTI reported.
Minutes after Gabbard's announcement, Republicans released a "cheat sheet" about the Hawaii congresswoman dubbing her "Assad's mouthpiece in Washington".
Gabbard's aide Rania Batrice will manage her presidential campaign.