what to write on christmas card for coworker

Well, that depends on the relationship you have with your coworker. If you're on good terms, you could write something like "Happy holidays! I hope this year brings you joy and success in all your endeavors. Best wishes for a wonderful new year." If you're not too close with your coworker, you could keep it simple with something like "Wishing you a happy holiday season." Whichever route you take, it's always nice to personalize your message to reflect your relationship with the recipient.