How do you handle an employee that's proving to be a poor culture fit?

Get rid of em, the sooner the better. You are doing yourself, and the employee a disservice by keeping them around.

First ask yourself: "Have I clearly defined our company's culture with a set of written Core Values?"

If the answer is no, then do that first. (create a document)

Next list everyone's name on a spreadsheet and have a column for each cultural core value.
Rate each employee as a:
1- typically does not display this Core Value
2- sometimes displays this Core Value (but typically not when under pressure)
3- usually displays this Core Value

Ask each employee to rate themselves and to rate you. (You do the same for each of them). Then have one on one meetings, and be clear that you are having them with everyone and that everyone has opportunity for growth, including yourself.

When you meet with this individual follow this pattern:
1) This is what I am experiencing
Provide one or two examples. Remember this has nothing to do with Task Execution...most employees who are a poor cultural fit will revert to listing of the task lists that they are good at executing. Remind them that this has nothing to do with Task Execution, something you are pleased with. But the position at the company is equal parts Task Execution + Core Value Alignment. Today you are only speaking about Core Value Alignment.
2) This is my contribution to the problem
This is probably not a new problem. Your contribution may simply be that you have noticed this issue for awhile and failed to address it. Apologize for not communicating it sooner because if you had then this could already be resolved by now. Let the employee know that from this point forward you are completely committed to helping them achieve Core Value Alignment
3) Tell the employee what is at stake.
If core value alignment isn't important to them, then it isn't the right fit to continue working here. You will really miss the abilities they have brought to the table but since that is only half of the equation then you both will need to move forward. You believe that someone with their abilities can be a tremendous asset to the company if Core Value alignment is achieved.
4) Tell the employee how you will help them resolve this
-"I am asking for this to be better, and I am going to hold you to a pretty high standard so that over the next 4 weeks you can completely align with our company Core Values. Are you ok with that?"
-"I get the feeling this is Solvable (or Not)"
-"I get the feeling that this is a change that you need to make and not me, is that accurate?"
-"I do not want to force you into anything. If you choose to work towards aligning yourself with our company's Core Values then I want to support your plan. I want you to share with me a 1 page plan that outlines areas within the Core Values that need your attention and states a plan for growth"
*NEXT set a timeline: "I would like to support you in getting this started right away, would next monday be too soon to have this written out..ok can we agree on next wednesday then? Perfect, I will look forward to meeting with you next wednesday to review your plan" (THEY OWN IT!! very important)

5) Ask for feedback!
"Please share with me your thoughts and opinions regarding what we have spoken about today, I AM Listening"
*SEEK TO UNDERSTAND instead of just telling him/her everything..do Not seek to be understood.
-"Why do you think you have given this impression?"
-"Do you think there is anything you do that might make someone feel like you didn't value this Core Value?"

THERE WILL BE PUSHBACK: Hardworking employees who lack Core Value alignment will pushback hard with how effective and good they are. IT IS IMPORTANT to acknowledge that they: Are an important employee, they do make a big contribution. But tell them that "You are measuring in terms of results, but I am speaking in terms of values"

I have had this conversation 4 times. 2 times the person saved their own job and are Still employed by my company. 2 times the person came to the conclusion that they did not fit our company any more. There was a strong paper trail, and the separation was clearly based on Values instead of Results...which can help you support your reasons for firing should there be any repercussions.

WHEN FIRING:
ALWAYS: seek to honor the good things that have occurred as a result of their employment
NEVER: say that this is really hard for you, that is a selfish statement, this is their time to grieve the loss of a job. It is not comforting even though that is the intention of your comment.

I really hope this helps!! It is a hard step to go through but doing this well can have a positive effect on every other employee on your team. Since they each had a meeting with you as well...it underlines the importance of Core Value (Cultural) alignment and unifies the team.

You address it immediately and help that person find a more appropriate fit. You'll both benefit in the end. Don't feel guilty - the faster you sort out who adds value around you, the faster you'll get to where you want to go. The only way you find this out is by trying each other out. It takes a great leader to recognize there is culture fit - and you can be sure you will recognize this in interviewing future candidates and not make this mistake ever again.

Kelly is right, address it immediately. I also recommend you read Alex Turnbull, the founder of Groove, blog about it at https://www.groovehq.com/blog/how-to-fire-an-employee

You should talk to the individual and try to find out what's creating a poor fit. On another note, cultural fit is often discriminatory in practical scenario. Hence, I would like to know what's your definition of "Culture" and "Culture Fit" before advising anything further. Perception in such cases could easily get driven by stereotypes.

Would, also like to see your sanity checklist. Hope above helps!!

i've been in such situation..
So just tell hir so. If you're in generous mood, give hir a week (or 2?) to switch. But it'll probably be a waste.
btw, consult the team about it. If they also say s/he's more trouble than helping, then bye-bye. You cannot afford "negative" performance - someone reducing others performance in this or that way. The team might be better without hir - more work to do but at least no fake stuff..

The firsts thing to try to do is reach out the employee and see if there are issues with communication or expectations that can be resolved to help the employee be a better fit. From there if the problem isn't solvable I would start to slowly isolate the employee and manage them out. If they do anything that impacts the integrity of the business or are preventing you from properly moving forward, terminate.

That is always difficult. In my experience that can be a killer in a small environment in many ways. I suggest dealing with it quickly and honestly. Do you see an opportunity for the person to adapt or is there no hope? Sit down with the person outside the office to have a genuine conversation about your concern and hear them out. It may be appropriate based on the outcome of your discussion to give a certain time period to allow them to implement your feedback, or it may be best to part ways quickly. Either way, always remember that leaders get the behavior they tolerate, good or bad. Nipping this in the bud will help the team members who are a great fit see you value their input and keep them motivated.

Best of luck!