Afi Farma has been linked to the deaths of more than 200 children
They were handed two-year prison sentences and fined 1bn Indonesian rupiah ($63,029; £51,7130).
The firm, Afi Farma, was accused of producing cough syrups containing excess amounts of toxic substances.
The company's lawyer said they denied negligence and the firm was considering whether to appeal.
Prosecutors had been seeking a prison sentence of seven to nine years for Afi Farma's chief executive, Prasetya Harahap, and seven years each for the other defendants.
The Public Prosecutor said that between October 2021 and February 2022 the company received two batches of propylene glycol, which is used for making cough syrup.
These batches contained 96% to 99% ethylene glycol, the prosecutor said. Both substances can be used as additives to solvents. While, propylene glycol is non-toxic and widely used in medicines, cosmetics and food, ethylene glycol is toxic and used in paint, pens and brake fluid.
The company did not test the ingredients used in the cough syrup and instead relied on quality and safety certificates from their supplier, prosecutors said.
Afi Farma's lawyer, Samsul Hidayat, told the BBC that Indonesia's drug regulator did not require drug makers to carry out rigorous testing of ingredients.
The judge in the Kediri District Court, East Java, found the four defendants guilty of intentionally producing pharmaceutical goods that did not meet safety standards.
The case comes as efforts grow worldwide to tighten the oversight of drug supply chains after the poisonings.
Since 2022, more than 200 Indonesian children, most of whom were under the age of five, have died of acute kidney injury linked to contaminated cough syrup. About 100 deaths have been reported in The Gambia and Uzbekistan.
The World Health Organization (WHO) has issued warnings about six cough syrups made in India and Indonesia.
-- Courtesy of BBC Sport