Two members of staff at the Tesco Extra supermarket in Culverhouse Cross have tested positive for coronavirus.
A spokesman for the company confirmed that a "small number" of its workers are now self-isolating after coming into close contact with the two infected people.
He added that Tesco continues to comply with all public health guidance and track and trace requirements.
Despite the cases being identified, the supermarket on the outskirts of Cardiff remains open to customers.
"A small number of colleagues at our Culverhouse Cross Extra store are self-isolating after two colleagues tested positive for Covid-19," the spokesman said.
"The safety of our colleagues, customers and suppliers remains our number one priority and we are following all government guidance and taking the relevant precautions.
"We have extensive measures across all of our stores to help keep everyone safe, including protective screens at every checkout, social distancing measures and regular deep cleaning."
Last month, Talbot Green Tesco, based in Rhondda Cynon Taf (RCT), was one of six supermarkets told to improve their coronavirus safety measures or face closure.
The supermarket was criticised by RCT Council for not ensuring that social distancing was being maintained and that hand and cleaning sanitiser was available where appropriate.
After being issued an improvement notices by the local authority, steps have now been taken to improve its infection prevention and control measures.
