Pro-choice supporters are praising the vote, saying the measure went too far.
If passed, the so-called "personhood" proposal would have made common forms of birth control illegal and forced women to carry unwanted pregnancies to term.
The initiative was rejected by more than 55 percent of Mississippi voters, falling far short of the threshold needed for it to be enacted.
Supporters of the measure said they were trying to create a legal challenge to Roe v. Wade, the 1973 Supreme Court decision that established a legal right to abortion.
They're hoping to get similar measures on the ballots of several states, including California, next year.
The Associated Press contributed to this report.