Upton was born in St. Joseph, Michigan,and raised in Melbourne, Florida.She is the daughter of Shelley (née Davis), a former Texas state tennis champion, and Jeff Upton, a high school athletics director. Her uncle is U.S. Representative Fred Upton (R-MI). Upton’s great-grandfather, Frederick Upton, was co-founder of appliance manufacturer and marketer Whirlpool Corporation.
Upton attended Holy Trinity Episcopal Academy. As a young equestrian, she showed at the American Paint Horse Association and competed at a national level.With her horse Roanie Pony, she won three APHA Reserve World Championships — 13 and Under Western Riding, 13 and Under Horsemanship, and 14–18 Western Riding. She was named the 13 and Under Reserve All-Around Champion, giving her a total of four reserve championships (2nd place). In addition, Upton ended up third overall on the APHA youth Top Twenty.With a second horse, Zipped, she won 14–18 Western Riding and was included in the top 5 in 14–18 Horsemanship and 14–18 Western Pleasure in 2009.
Upton has expressed that her belief in God is important to her. During a photo shoot, someone joked about a cross necklace she wore, « Why are you wearing a cross? Like you would be religious, » then took the necklace from her to do the shoot. Upton stated about the incident: « I was really affected by that. The whole thing made me realize that I do want a cross with me, at all times. » As a result, Upton had a cross tattooed on the inside of her finger.