Artie Decker is fired as an announcer for the Fresno Grizzlies baseball team because he is not up on new technology and doesn't know how to use it. Artie is disappointed because he loved the job.
Meanwhile, in Atlanta thousands of miles away, Artie's daughter Alice Simmons and her husband, Phil, want to go on a business-related vacation. Alice is not able to get her husband's parents to look after their three kids, she reluctantly asks dad Artie and mother-in-law Diane for their help. This was a last resort, since she thinks they are "weird."
Artie and Diane agree to come take care of the grandchildren while their parents (type-A helicopter parents) are in North Carolina for a few days. Artie tells the kids to call him Artie and never "Grandpa". He is quickly nicknamed Fartie by the youngest child, Barker, who is defiant and cheeky.
The only girl, Harper, is very tense due to her preparation for a upcoming violin audition. Diane advises her granddaughter to have some fun and not take the audition too seriously, exactly the opposite of Alice's parental advice.
The older grandson, Turner, is having trouble in school with a bully, so his grandfather encourages him to stand up for himself, resulting in a black eye. Artie creates havoc at Turner's Little League baseball game as well.
Diane is determined to prove to Alice and Phil that they aren't just the "other grandparents." Problems arise when the kids' 21st-century behaviors collide with Artie's and Diane's old-school methods. And distracted by the possibility of finding a new job with the television network that employs his daughter, Artie makes a spectacle of himself at a skateboard competition and the violin recital.
But by the time Alice and Phil return, in a panic, they find that Artie and Diane have been able to earn the trust and love of all the kids.