Little did he know that within two months, he would've won 120,000 followers - as people from all over the world signed up to hear regular stories about Betty's battle with cancer.
Zach, who is from Louisville, Kentucky, started the Instagram account after the family were given the devastating news that Betty was suffering from terminal lung cancer.
And at 80-years-old, Betty was sadly deemed too weak to undergo chemotherapy or other forms of cancer treatment, so was sent home.
But despite these tragic circumstances, 15-year-old Zach decided to cheer his grandma up everyday, by posting pictures of her on the internet - winning her thousands of followers.
According to the family, Betty looks forward to her Instagram updates each day, and she has become something of a celebrity since the account was set up.
She's been featured on local news, and Betty says she gets happier every time she has a new follower.
Zach also added that the Instagram means he's spending lots of time with his grandma, and is creating memories he can cherish forever.
The family received a huge surge in followers after Pharrell Williams became one of Betty's first followers on the site.