An electronic device and an antenna structure thereof are provided. The antenna structure includes a first, a second and a third radiating element and a grounding element. The first radiating element includes a first and a second radiating portion, a feeding portion and a grounding portion. The grounding portion includes a first, a second, a third, a fourth and a fifth section. The first section is connected between the first radiating portion and the feeding portion. The grounding element is connected with the fourth section and the fifth section. The second radiating element is connected with the grounding element. The second radiating element includes a third radiating portion, and the third and the second radiating portion are coupled with each other. The third radiating element is connected with the feeding portion, and the third radiating element and the first section are coupled with each other.