The Poland international has moved to Southampton's south-coast neighbours on until January, it was confirmed on Friday.
Boruc made 29 Premier League appearances last season but has since been usurped by Fraser Forster, who arrived from Boruc's former club Celtic.
The 34-year-old is yet to feature in any matchday squad under Ronald Koeman, with Kelvin Davis preferred as understudy to Forster.
Boruc trained with Eddie Howe's men on Friday and is available for Saturday's trip to Watford.
He is also eligible for Bournemouth's League Cup third-round clash at Cardiff City on Tuesday, having not featured in Southampton's 2-0 win at Millwall earlier in the competition.
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