Legal Question in Business Law in California

A settlement agreement is ineffective against any party that hasn't signed it. Whether the absence of that party's signature renders the entire agreement ineffective is a question that cannot be answered with certainty without reading the document, but it's very possible that, lacking a party's signature, the settlement agreement doesn't bind anyone. Consult a lawyer to be sure.

All parties need to sign if you want the settlement agreement enforceable by way of the procedures set forth in Code of Civil Procedure section 664.6.

I disagree entirely with Mr. Whipple. If one defendant settles for themselves AND the benefit of the other defendant, signs the settlement and complies with the settlement terms, I see no reason that a binding third-party beneficiary contract for release of both defendants is not formed and enforceable regardless of whether the second defendant signs it or not. Now if the terms of the agreement are tri-lateral and the second defendant never signs it, that is another story, but the mere fact that the second defendant did not sign does NOT automatically make the release unenforceable as to that second defendant.

If you are in a civil lawsuit, and you have an attorney he or she should advise you about the settlement agreement. If you don't have an attorney, you should consult with one before you sign anything. As a point of information, it is possible to release someone without their signature, but you would want them to release you as well. In order for them to release you, they would need to sign. In a settlement agreement, it is not a good idea for one person to be released without giving something in return.