The site will be opening tomorrow (August 24) and The News was invited down to get an exclusive look inside today.
Leader of Portsmouth City Council Steve Pitt said: "I am delighted to welcome Wendy's to Portsmouth's Commercial Road. This is a positive step forward in the regeneration of the city centre and a good indication of our potential to attract quality inward investment to develop our high street to benefit our local economy.
"Wendy's is a well-known and respected brand, and their decision to open a restaurant in Portsmouth is a vote of confidence in our city. Their arrival will help to attract more visitors and businesses to the area. We are committed to regenerating the city centre and creating a vibrant and attractive place to live, work and visit. "
The venue will also be offering the first 30 customers a Bacanator combo for free tomorrow and it is expected to be busy over the next few days.