I became my dad's healthcare PoA in 2021. Just found a document that he appointed my mom as his healthcare POA in 2016. How do I proceed?

Bryant,

1. Validity of current document(s). The last law firm I worked for with a strong EP, Trust and Probate practice ALWAYS included in any granting document (POA, DPOA, Trust, etc.) the phrase stating that :

"this document supercedes (and renders ineffective, if I remember correctly) any previous POA, DPOA (or whatever the document was" executed by _________ "(name of individual creating the document).

Check for that wording in the 2021 document you have. If it contains a rescission of terms in the 2016 document, or any other document, then the 2021 governs.

2. Trusts are different though, in terms of updating and changes, and can be done by changing the specific issues, quoting the old provisions and providing the newer ones which render the older ones ineffective.

3. Alva raises a critical issue: state of mind and cognition when the second document was enacted. In my experience (at that last firm mentioned), the attorney typically asks the family to leave the room while she/he confirms the intents of the individual requesting document changes, but also observes for mental clarity.

4. As Grandma1954 notes in her first post, the newer document should be replaced with any entity that received a copy of the executed first document. That might be hard to determine though, unless there's a distribution list. You might just provide a copy of the executed current document for clarity to all those who you believe need it.

5. You wrote:

"... My mom had no idea she was his healthcare POA. Would she have had to have been present? Her signature is not here. Just my dad's, his PCP, and a witness.

So looking at the document closer it is a "Advance Directive" power of attorney.

Does this mean it only takes effect if he becomes unable to communicate his wishes?"

Based on my experience, someone agreeing to act as any kind of proxy needs to agree to that role. There should be an acceptance in the signature area, and your mother's signature should be there, and should have been notarized.

My experience is that an Advanced Directive is more of a guideline/direction for healthcare decisions but it can also be considered a Living Will. Whether or not it's keyed to specific health issues depends entirely on the provisions contained in the document.

There's no way we can advise if it's effective w/o knowing what provisions are contained, which are enumerated, whether or not medical stages are addressed and/or what action could or couldn't be taken.

You override her. But do know that if he has dementia and gave you POA while demented, it isn't valid. To grand POA to anyone you have to be of sound mind. In that case the latter POA could be challenged by the wife.
In most circumstances I am guessing you and Mom agree???
But there may be some. Say, Dad has dementia, and enters hospital with Covid-19, needs to be put on ventilator. Mom refuses and you want to do it. She says "I have POA; he was of sound mind when he told me he never would want to live longer if demented, and to make him DNR and never uses vent."
and YOU say "NO, I have POA and mine was most recently done; I want all heroic measures to keep my Dad alive".
IF she challenges the POA in court and it can be proven Dad had dementia when he gave YOU POA you will lose. The question is, will she go that far.
So you can see the issues here.
If Dad was still competent to give you POA in 2021, then you are POA for certain. Do you anticipate argument with Mom?
And yes, a POA advanced directive only becomes in effect when the principal, the person who gave it, cannot speak any longer or is incompetent to fulfill his wishes. As long as Dad can make his own decisions he can make them even if they don't match wishes written BY HIM into an advance directive. That is he can change his mind about any care as long as he is competent and as many times as he wishes.

Bryant, he gave you the tough "job" making final decisions when it comes to end of life. Probably knowing it would be difficult for mom.
(I would have to rethink the CPR though.. Breaks Ribs, fractures the sternum and rarely works. If you can talk to him about this, but that is my opinion)
By the time you will need the Advance Directive he probably will not be able to communicate his wishes either because of the dementia and not comprehending what is being asked or he will not be able to communicate for a variety of reasons.
Actually if he comprehends things now you can discuss a POLST with him, it is more detailed than the old DNR and it goes into more explanation of each phase of possible measures that might be taken.
As he declines please consider Hospice. My Husband was on Hospice for almost 3 years and they were amazing. The care he got, the compassion from the Nurse that saw him each week to the CNA that saw him several times a week. And I got support as well!!!
He knows you will do the right thing. Never doubt yourself. Any decision you make with his best interest at heart is the right one.

I would think any more recent document would override any previous one.
Just curious is mom Cognizant? Still married to your dad? have you told her that you are POA? What was her response?
IF he informed anyone of the previous POA anyone that legally needs to know about the POA should be informed of the new one. (Banks, Financial Planner,...)

**side note, your dad is so very young. My Husband was diagnosed when he was in his early 60's. Not easy. (If he is a Veteran contact local Veterans Assistance Commission and see if he qualifies for any help from the VA Veterans Assistance Commission of Cook County 312-433-6010.
https://vacofcookcounty.org)