The glamour model arrived in the famous gambling city earlier this week and now the Argentinean hunk has jetted in so they can spend some quality time together.
The loved-up pair - who got engaged last month while on holiday - spent yesterday (16.05.12) lazing around the swimming of their hotel while working on their tans.
While Vegas is known for its quickie wedding ceremonies, it is not thought Katie and Leandro will tie the knot there, especially as she married second husband Alex Reid at one of the city's chapels in February 2010.
Katie and Alex wed in Vegas after a whirlwind romance, following her split from first husband Peter Andre in 2009, but broke up just 11 months later.
Their divorce was finalised in March, one month before she announced her engagement to Leandro.
The 33-year-old beauty has two children, Junior, six, Princess, four, with first spouse Peter, while she also has a nine-year-old son Harvey from her relationship with soccer player Dwight Yorke.
In March, Katie claimed she was single despite being regularly seen with Leandro.
She said: ''I'm single. But he's still around but he's one of these people who when we go clay pigeon shooting and when I win he's very touchy and I'm like 'get off Leo'. So no, it's a laugh and he is about but I am single.''