The lyrical themes of Practice What You Preach are more about politics and society than the occult themes of the band's previous two albums. The title track of this album was a moderate mainstream rock hit, which featured a music video that gained substantial MTV airplay, as did "The Ballad". By June 1992, Practice What You Preach had sold over 450,000 copies in the U.S,
Reviews for Practice What You Preach have generally been favorable. Allmusic's Alex Henderson awards it three stars out of five, and for the album, he claims that Testament placed "more emphasis on subjects like freedom of choice, political corruption, hypocrisy, and the effects of greed and avarice" and that "its musical approach is much the same -- under the direction of metal producer Alex Perialas."
Practice What You Preach entered the Billboard 200 album charts in September 1989, a month after its release. The album peaked at number 77 and remained on the chart for twelve weeks.
Testament toured for less than a year to promote Practice What You Preach. They embarked on a one-month U.S. tour in October 1989 with Annihilator and Wrathchild America (who had just released their respective debut albums Alice in Hell and Climbin' the Walls), and played two shows in California with Nuclear Assault and Voivod in December. The second leg of the Practice What You Preach tour began in January 1990, when Testament was supporting Mortal Sin in Germany and the UK with Xentrix and Horse London. Following their first visit to Japan in February, Testament embarked on a two-month U.S. tour with Savatage, which featured support from Nuclear Assault, Dead Horse and Dark Angel. After the Practice What You Preach tour came to an end in May 1990, Testament began work on their fourth studio album Souls of Black.