Tylenol and Advil work by different mechanisms. Doctors will often say to take them a few hours apart. It depends on the reason you are taking both medications but to be on the safe side ALWAYS ask a doctor or a pharmacist. If your doctor tells you not to take both together he/she would have a good reason for giving this advice.

According to my doctor a few years back, yes. They way each works is sufficiently different that they don't get in each other's way, and can complement one another. I don't do it routinely, but for really bad pain, like if my back goes, I'll use the combination.

I AM NOT A PHYSICIAN. THIS IS NOT MEDICAL ADVICE.