Maruha Nichiro Holdings announced earlier this month it was recalling products after some were found to contain high levels of malathion.
The pesticide is used in farming, gardening and for killing fleas.
Up to 2,800 people reported symptoms after eating the products, which included pizza and chicken nuggets, manufactured at a factory in Gunma prefecture, north of Tokyo.
Police say they arrested Toshiki Abe, 49, a worker at the subsidiary of Maruha where the tainted food was found, on Saturday.
He is suspected of putting the pesticide in frozen foods at Aqlifoods’s Oizumi plant in Gunma on four occasions last October.
Mr Abe has denied the charges, police say.
Maruha, which has received hundreds of thousands of phone complaints, issued public apologies in full-page ads in newspapers and warn people not to eat any of the possibly tainted food.