Is 120 pounds considered underweight for a person who is 5 feet, 7 inches tall?

Yes, but 123 isn't. I just checked. Also it depends on your age. I am 62 and at 122 and 5 feet 7 inches I am considered underweight.

If you use the BMI Calculator on mayoclinic.com- you are just on the edge of normal weight. Some people are naturally thinner and have a smaller bone structure. That being said, I concentrate on eating healthy,nutritious food and know when I feel over or under weight and healthy. Eating healthy and getting moderate exercise are more important than what the scale says.