Videomaker – Learn video production and editing, camera reviews › Forums › General › Open Forum › Can I promote my freelance business using video I created at previous employer? › I’m not an attorney. That
I'm not an attorney. That said, according to my reading of the U.S. Copyright law — https://www.copyright.gov/circs/circ09.pdf — you created what is known as a "work for hire." As such, the copyright belongs to your employer unless you and he agreed in writing to the contrary. So the answer would be "no," you don't have the right to use the material you worked on.
I would speak with the former employer to see if it's o.k. with him for you to use the material. Point out that you will give credit to his company in your reel and that he will be getting what amounts to free advertising. Let him see the reel before your post it anywhere so he can see how good you've made him and his business look and so he can see there is no proprietary information being disclosed. If it were me, I would go on camera at the beginning of the reel and say "I'm Joe Smith and much of what you're about to see was developed while I was employed for five years as videographer and editor at the Bob's Your Uncle tractor plant in Spider's Breath, Wyoming."