The job of the marshals is to advise and support members of the public by reminding them to follow guidelines.
They do not have any formal enforcement powers, but they will be connected by radio to police and coronavirus response sources who do have those powers.
The marshals will be wearing high-visibility blue jackets and will operate across Barnsley seven days a week - until 10pm on weekdays and 8pm on weekends.
Coun Jenny Platts, cabinet spokesperson for adults and communities, said: “Having the Covid marshals in place is another step forward in our response against coronavirus.
“We hope they will be able to take some of the pressure away from police and council officers, who have worked tirelessly through the pandemic.
“While they are there to help, we all need to continue to play our part in limiting the impact of the virus and saving lives.
“This means following the guidance in place regarding social distancing, wearing a face covering unless exempt and washing or sanitising our hands regularly.”