Here’s a short, useful story that answers the question while illustrating why TV character ages can be confusing. The Case of Mandy’s Missing Birthday

“But wait,” Claire adds, “that episode aired in 2023. The show’s timeline moves slowly. By the end of Season 7, she’s still 29 or just turned 30. Meanwhile, the actress, Emily Osment, was 31 during filming. See the confusion?”

When you ask “how old is Mandy from Young Sheldon ?” the answer is 29 for most of her run (from late Season 5 through Season 7). But her age feels fuzzy because TV shows stretch time, actors age differently than characters, and later spinoffs ( Georgie & Mandy’s First Marriage ) may tweak ages for story purposes.