Barnardo's will close its South Street shop and aims to open in larger site in North Street in October.
Signage for the charity shop has already begun appearing in North Street between Holland and Barrett and Marks and Spencer, taking the place of the former Wallis store which closed down earlier this year.
Kay Fisher, store manager, said: "We have been in Chichester for 25 years and our lease is up so we decided to go for a bigger and better store and we are excited for it.
"We have got really good support here and we love being in Chichester."