With Augsburg beating Hamburg, a point for Hoffenheim leaves them four points behind the Bavarians, who occupy the relegation play-off berth, and nine points adrift of safety with only seven games to go.
Mainz move up to sixth in the table, taking advantage of Hamburg's defeat.
Mainz could have taken the lead in the 17th minute when Nikolce Noveski headed against the post from Alexander Ivanschitz's free-kick.
The home side gave no impression that they were a side fighting for their lives at the bottom of the table and desperately in need of points with very few attacks - and even fewer openings.
The closest they came to testing Christian Wetklo in the Mainz goal was in the 26th minute, but Kevin Volland's shot was deflected off target by Noveski, who repeated the feat to deny the same Hoffenheim player early in the second half.
A mistake by Noveski allowed Joselu to bear down on Wetklo, but he lacked support as the chance went begging.
Mainz seemed happy enough with a point and prevented Hoffenheim from creating any real danger.
They then broke almost to steal all three points with Zdenek Pospech's shot grazing the outside of the post on its way wide as the game remained goalless.
Hoffenheim coach Marco Kurz went all out attack in the last 10 minutes with Igor de Camargo brought on, but he could not alter the scoreline.