Celebrity Millennium completed an extensive bow-to-stern modernization at Sembawang Shipyard as the first vessel transformed under Celebrity Cruises' $500 million Celebrity Revolution fleet-renewal program. All staterooms and suites were redesigned, 30 new accommodations were added, and suite areas were enhanced with the new Retreat Sundeck and redesigned Retreat Lounge. Restaurants, bars and lounges were reimagined, while the spa, casino and retail areas were extensively renovated. Accommodations received new furnishings, finishes and Celebrity eXhale bedding along with RFID locks, Bluetooth capability and upgraded connectivity, bringing the ship's design and guest experience closer to the newer Celebrity Edge standard.

Celebrity Millennium completed an extensive three-week transformation at Grand Bahama Shipyard as the fourth and final Millennium-class vessel to undergo Celebrity Cruises' $140 million “Solsticizing” fleet-renewal program. The project added new staterooms and introduced 107 AquaClass accommodations with access to the new Blu restaurant, while Celebrity Suites received new private verandas. New Solstice-class venues included Qsine, Celebrity iLounge, Bistro on Five, Café al Bacio and Gelateria, Cellarmasters, and the Martini Bar and Crush. Public spaces and accommodations received extensive new carpeting, upholstery, furnishings and décor, while shipwide Wi-Fi and other technology were upgraded.