The opening event was hosted by world cup rugby player Ben Cohen, who was joined by VIP guests to celebrate the launch of the spa and four new suites.
Singer Vijay Prakash, whose songs featured in the movie slumdog millionaire, also attended the event.
The 85-bedroom hotel is a grade II-listed regency crescent terrace with a beach-front location overlooking the English Channel.
Kanagaratnam Rajaseelan, managing director, said that the investment had created around 25 jobs, including therapists, gym instructors and receptionists, providing a “major boost” to the economy of Dover.
He added: “Everyone who has been involved in this exciting project deserves huge credit. It has been a labour of love and we are delighted with the results.”