The 21-year-old actress, who plays big-eyed teenager Haley Dunphy on the hit ABC comedy, told ABC's "Good Morning America" for a report aired Monday that she had the surgery in April,
At age 9, she was diagnosed with abnormal kidney development. The condition often left her exhausted or in pain. But as her health grew worse, she began seeking an organ donor. Her father, actor Edward James Hyland, was a match.
She says she tells her dad, "It's weird - I've got your kidney in me."
Hyland plans to spend the show's summer hiatus recovering from her surgery.
Her secret struggle is also reported in the current issue of Seventeen magazine.