Staff challenged the pair at Sainsbury's, Reedswood Waym Walsall.
Officers have issued an appeal for information but did not reveal when the incident happened.
Walsall Police tweeted: "Do you know this pair?
"We want to talk to them about an attempted theft at Sainsburys in Reedswood Way, Walsall."
The police added: "A man and woman were challenged by staff after money was stolen from a till.
"Can you help? Please get in touch via 101 or Live Chat quoting 20/310386/23."