Do I listen to my manager or the boss?
What is happening here?
When a boss, who I assume in this scenario, is the company’s owner or CEO, counteracts a manager’s decision he either believes the manager’s directive was flawed or he has a negative need to control situations. In a perfect world if a manager is incompetent a boss should deal with that manager directly rather than coerce an employee into overstepping their manager. Nothing will ruin an employee/manager relationship faster than being perceived as going over your manager’s head. Let's assume this boss has a negative power need to control situations.
What should this employee do?
Ultimately an employee answers to the boss, so you will have to listen to him or her, but you should talk to your manager first. I suggest the “I perceive,” “I feel,” “I need” communication technique I learned at an assertive communication seminar:
In situations where you’ve instructed me to do xyz, Mr. Boss has told me to do abc.
I am confused and unsure how I should proceed.
I need you to understand my predicament and to help me determine which approach I should take.
If the boss continues to overrule your manager’s decisions have the same conversation with him. Your boss and manager need to work this out and stop placing you in this position.