In Northern Ireland, can i drive my dads car if he's with me, as long as i have a provisional?

Yes, as long as you are at least 17 ,you can, and yes you most definitely need car insurance.

Your dad could add you to his insurance as a named driver, which probably wouldn't be TOO expensive....maybe.

Remember, your dad needs to be with you at all times and all the laws which apply to a driver also apply to someone accompanying a learner driver.

For instance--

If, while you're driving, your dad uses his mobile phone whilst sitting beside you , he will be prosecuted for the offence just as he would if he were driving the vehicle himself.

Obviously the same applies to drink driving.

HTH

If your dad has 3 years or more driving experience and YOU are on his insurance policy then yes you can drive his car, but ONLY if he is in the car with you.