Armstrong played the trumpet so powerfully that he often split his lip.

The nicknames "Satchmo" and "Satch" are short for "Satchelmouth". The name has many possible origins, but the most common tale involves Armstrong dancing for pennies as a young boy in New Orleans. According to biographers, he would scoop the coins off the street and stick them in his mouth to prevent bigger children from stealing them.

He was skilled at scat singing (improvised vocal jazz using nonsensical words) and was among the first to record it, on the Hot Five recording "Heebie Jeebies" in 1926. The recording was so popular that his group became the most famous jazz band in the United States.

Armstrong spent his youth singing on the street for spare change, but he didn't receive any formal musical training until age 11, when he was arrested for firing his stepfather's gun during a New Year's Eve celebration. He spent the night at New Orleans Juvenile Court and was sentenced the next day to detention at the Colored Waif's Home for Boys. It was there that Armstrong learned to play the bugle and cornet from the Home's music teacher. Armstrong would later write, "I do believe that my whole success goes back to that time I was arrested as a wayward boy."

He wore the Star of David in honor of the Karnoffsky family, who took him in as a child and lent him money to buy his first cornet.

In 1930s Hollywood, black actors were not filmed singing to each other, so Armstrong sang it to a racehorse named Jeepers Creepers. The phrase "jeepers creepers", a euphemism for Jesus Christ, predates both the song and film.

His most familiar role was as the bandleader/narrator in the 1956 musical High Society. He appears throughout the film, sings the title song, and performs a duet with Crosby called "Now You Has Jazz".

Armstrong used laxatives to control his weight, a practice he advocated both to acquaintances and in the diet plans he published under the title Lose Weight the Satchmo Way. His laxative of choice in his younger days was Pluto Water, but when he discovered the herbal remedy Swiss Kriss, he became an enthusiastic convert, extolling its virtues to anyone who would listen and passing out packets to everyone he encountered, including members of the British Royal Family.

"What a Wonderful World" was first released as a single in 1967 but performed poorly in the United States, selling fewer than 1,000 copies. The song didn't make a comeback until 1987, when it was included in the soundtrack of Good Morning, Vietnam and re-released as a single. It rose to number 32 on the Billboard Hot 100 and has been considered one of Armstrong's signature tunes ever since.

Although he avoided politics for most of his career, Armstrong made national news in 1957 when he criticized President Eisenhower for his inaction during the conflict over school desegregation in Little Rock, Arkansas. "The way they are treating my people in the South," he said, "the government can go to hell!"