The tin collecting money for the Royal British Legion was stolen from the White Lion Hotel in Claremont Road, Seaford, on November 14 around 12.30pm.
Two women entered the pub while the bar staff briefly entered the kitchen area, one of the women picked up the tin and put it in her handbag.
Police constable Russ Watson said: “These two women entered the property and one of them asked to use the toilet while the other sat at the bar.
“While the staff member had their back turned and was going into the kitchen area, the woman at the bar picked up the tin and put it in her bag. Both women left immediately afterwards.
“Any theft is unacceptable but stealing money from a charity is particularly abhorrent.
“If you have any information on who these women might be please get in contact with us immediately.” To report any information call 101 quoting referance 502 of 16/11.