The bill, which Republican majority leaders have called one of their top priorities this year, seeks to undo several judicial changes that have been made to the Missouri Human Rights Act.
Under current judicial interpretation, an employee in Missouri must only prove that his or her race, gender, sexual orientation, religion, physical handicap or other protected status was a "contributing factor" in adverse employment actions made against them.
But Senate Republicans want to revert to the standard established in the 1964 Civil Rights Act, where it must be proven that an employees protected status was a "motivating factor" in their employer's actions.
The bill was filibustered Wednesday by several Democratic senators from St. Louis and Kansas City who said the bill would reverse years of civil rights progress in Missouri.
"I don't want to pass a piece of legislation that undoes decades of progress for African Americans in Missouri," said Sen. Maria Chappelle-Nadal, who led the filibuster.
Senate Republicans argue the bill will put Missouri in line with other states in terms of discrimination law, making the state more attractive to outside businesses. Gov. Jay Nixon vetoed a similar bill last year.
The filibuster temporarily came to an end Wednesday evening, without the bill coming to a vote. Debate is expected to resume next week.