The 19-year-old pop superstar sent his devoted fans into a frenzy yesterday (19 November) by uploading a photo of himself receiving a peck on the cheek from the blonde beauty.
But before the Beliebers could assume that this was Justin's latest love interest, he wrote the caption: "#allthatmattersmusicvideo".
(Although, he did post the picture twice in a row!)
The cute snap shows Cailin wearing a revealing leather bra top and matching shorts, while pulling on Justin's thick silver chain and leaning in for a kiss.
Acting nonchalant about the pretty girl by his side however, Justin merely pointed at Cailin and kept his eyes on the camera lens instead.
He wore a plain white T-shirt, which showed off his tatoo sleeve, and a pair of diamond earrings.
Over the last few weeks, the award winning singer has been releasing a brand new track for fans every Monday, as part of his Music Monday series.
This recent material demonstrates Justin's growth in the industry and has a more mature R&B sound than his previous records.
'All That Matters' was a Music Mondays offering, which was released in October and despite the lack of airplay and promotion, it still managed to rack up 127,000 in its debut.
This Monday (18 November), Justin teamed up with R&B veteran R Kelly for the raunchy single 'PYD'.
As well as surrounding himself with female company on his music video sets, the chart-topper hosted a party at his house in LA last week and apparently invited TOWIE stunner Lauren Pope along.
And Justin was even said to have had the hots for Lauren all night!
The words 'kid in a candy store' spring to mind!
Listen to 'All That Matters' below and let us know what you think, as the best comment across the website each week wins £50!