Is one hair transplant enough to restore a full head of hair?

There are many variables needed to address the question if one hair transplant is enough they include: The size of the balding area being treated, the hair thickness (fine, medium or coarse), the color contrast between hair and skin (e.g. Blondes do better with less hair moved in proportion to the balding area), the character of your hair (straight vs very curly), your goals (are they realistic?), the experience of the doctor and his/her team, the density placed at the recipient area.  So if the bald area is small, then yes, one hair transplant can probably achieve reasonable goals.