The movie star – best-known for playing fashionista Rachel Green in Friends – wowed in the swimwear, showing off her tanned and muscular figure, looking very youthful for her 48 years.
The star headed out on to the balcony in the two-piece, taking a white dressing gown to cover up when the sun went in.
She got better weather on the balcony, surrounded by flowers, the previous day – when she was snapped rolling down her bikini straps to tan her shoulders properly.
Wearing dark Aviator sunglasses, with her long hair tied in a ponytail, the Hollywood actress seemed very relaxed and happy to be chilling out ahead of the new year.
The Friends legend arrived in Mexico just after Christmas with Justin, 46, via private jet – quashing rumours their marriage is on the rocks.
Their annual holiday is being shared by pal Jason Bateman and his wife Amanda Anka, who the actor recently claimed was groped by the owner of London bar Chiltern Firehouse.
In the lead-up to Christmas, Jen was seen shopping for presents back in LA, joined by a giant bodyguard.
The Horrible Bosses star also enjoyed a dinner with fellow Friend Courteney Cox, aka Monica Geller, this autumn.
It’s been 13 years since Friends ended but it’s clear that the two women are still close pals.