The woman in the video, believed to bet the monkey's owner, is heard shouting at the employee: "Let him go, let him go, let him go! If he bites you, they will put him down."
She then grabs the animal's leash and leads it away.
Ms Stewart's husband then tells the Wal-Mart employee: "You could have got hurt ... you could have got sick with that."
She told NBC4i.com: "I saw the monkey and he was just standing on the carts, and this lady was trying to come over and get him.
"The monkey had escaped from a nearby camper. And we saw the cart guy from Walmart coming over to help her.
"When we posted it on Facebook, we did it for fun. We go to Wal-Mart, we moved to Lancaster and there's a monkey."
She added on Facebook: "I think the woman was scared the monkey was going to bite him. So she pushed the guy away."
"It was crazy. We pulled up to Walmart and were like...is that a monkey?!?!? Haha."
Police confirmed they received a call from a woman, who described the monkey as being larger than her two-year-old. They said no criminals were filed against the monkey's owner.
A Wal-Mart spokesperson told NBC4 the employee was not bitten. Ohio's Department of Agriculture is attempting to track down the woman to confirm the animal is registered, the website adds.
The clip has racked up over 250,000 views on Facebook.
Last year, an escaped monkey damaged a police car and ate a woman's post after a rampage in Orlando, Florida.
While a US amusement park has previously been criticised for allowing this chimpanzee to allegedly smoke cigarettes and drink cans of fizzy drinks.
