I have a coworker with direct knowledge of a Military spouse cheating on her husband. What action, if any, should he take?

If so tell the service member and show the proof

Does he have evidence

If the spouse is cheating with a service member then he is violating the UCMJ. I would suggest you have your co worker report it to their chain of command.

None. In all honesty relationships are between two people and as much as strongly as your coworker might feel about this in the end it's none Of anyone's business. If your coworker and the husband are good friends maybe he should suggest going to a Chaplin but nothing more. Sometimes these couples stay together and the person who exposed the flaw is usually who they take their anger out on.

Hearsay doesn't count. It's very hard to prove adultry. There isn't anything that can be done to a civilian spouse. If the cheating spouse is military, unless he/she admits to it, it's still considered hearsay.

UNLESS THE COWWORKER HAVE DIRECT KNOWLEDGE THAT THE CHEATING WIFE'S ACTIONS ARE GOING TO CAUSE HER SPOUSE IMMINENT DANGER, MIND YOUR OWN LIFE BECAUSE, WE DONT KNOW THE WHOLE STORY OF THAT FAMILY'S LIFE. MAYBE HE'S CHEATING ON HER TOO AND SHE HAS DIRECT KNOWLEDGE OF HIM CHEATING ON HER TOO AND MAYBE THIS IS HER WAY OF GETTING BACK AT HIM. OR MAYBE HE KNOWS ABOUT IT BUT DOESENT CARE. OR MAYBE SHE JUST HAVENT GOTTEN CAUGHT BY HIM YET AND IF HE IS A SMART LEVEL HEADED GUY WHEN HE FINDS OUT HE WILL FIND THE COURAGE WITHIN HIM TO DIVORCE HER AS HIS WIFE. WE ALL HAVE PROBLEMS IN OUR LIVES FOR DIFFERENT REASONS THIS IS BECAUSE WE ARE NOT PERFECT BEINGS IN THE EYES OF EACH OTHER ON ANYTHING WE DO IN OUR LIVES.

Drive on. Not your buisness.

I would let the chaplain know in the unit, and I would also either tell the husband myself or have the chaplain do it.

Adultery and fratinization is a direct violation of UCMJ artical 134.http://www.military.com/spouse/relationships/military-divorce/legal-separation-adultery-and-ucmj.html esp. Considering rank of involved parties. The husband should be notified of the circumstances and let him take appropriate legal action. Even if he not in the military his spouse is and falls under ucmj artical 134

Most of the time nothing will happen. Unless you have proof and I mean in the act.