Democratic leader Harry Reid and Republican John McCain, longtime Johnson supporters, joined fellow boxing champions Lennox Lewis and Laila Ali, the daughter of retired boxing legend Muhammad Ali, in backing Tyson's petition on grassroots campaign website Change.org.
The petition says Johnson, the first black heavyweight boxing champion of the world "is long overdue a pardon. Johnson paved the way for black boxers like me."
"Thanks to @MikeTyson for joining effort to pardon Jack Johnson's racially motivated conviction," McCain said on Twitter on Thursday.
"One great boxer standing up for another," Reid tweeted on Wednesday.
Reid and McCain, along with Senator William Cowan and U.S. Representative Peter King, introduced a resolution calling for Johnson's pardon in March. Pardons require presidential approval.
More than 1,400 people have signed the petition since Tyson launched it Wednesday.
Johnson, the world heavyweight champion from 1908 until 1915, was convicted in 1913 for transporting a woman across state lines for immoral purposes. The law, meant to combat prostitution, was often used in the segregation era as a way to punish interracial couples.
Johnson, who was married three times, all to white women, was arrested in 1920 after seven years in exile and spent a year in jail. He died in 1946 at age 68.
At least two previous attempts to get Johnson pardoned have come to nothing in the past 10 years.
(Reporting by Eric Kelsey; Editing by Doina Chiacu)