The couple – who split in October after three years of dating – took a private jet to the French Riviera together on Thursday after the Don’t Hold Your Breath hitmaker finished a gig in Dublin, Ireland.
After heading off on a sightseeing trip around Monaco on a rented motorbike, the on-off pair spent two days holed up in a five-star hotel in the principality before emerging arm in arm.
Despite the apparent resurgence of their romance, the singer and the Formula One ace are said to be “taking things slowly”.
An insider told The Sun newspaper: “They looked so happy, it was sweet. They are taking things slowly and trying to avoid the same mistakes.
“They’re making sure they get every moment they can together.”
Lewis recently admitted he wouldn’t rule out reconciling with Nicole at some point in the future.
He said: “We still have very, very strong feelings for each other and I still love her very much. Who knows, maybe we will be together in the future?
“We’re friends and we can move forward. These times are sent to try you, it’s about how you pull through. I have my family who are helping, so I feel pretty good.”
Meanwhile, Nicole explained she still loved the sportsman “very much”.
She said: “Everything is very recent, so it’s a sensitive subject for me, but we are good friends and obviously we love one another very much.
“That’s where we’re at now and that’s a good place to be. What people see is completely opposite to what’s real.”