Traces of pesticides used to destroy insects and fungi were found during the tests conducted by Testfakta, a research company specialised in evaluating consumer products.
However, the levels do not exceed EU limits, newspapers Dagens Nyheter and Göteborgs-Posten reported.
Åke Bergman, an environmental chemistry professor at Stockholm University, told Swedish Radio News that there is a lack of knowledge about the combined effects of the "cocktail of chemicals" found in bananas.
"We know that pesticides are used in fruit and vegetables and of course they don't just vanish," Bergman said after studying Testfakta's findings.
None of the four organic banana kinds tested by Testfakta contained traces of pesticides, but they are also more expensive, costing around five SEK more per kilo than regular bananas.
On average, Swedes eat 19 kilos of bananas per year.