The Boyfriend singer has splashed out just over $6m on the 836m² property, an affluent area in the San Fernando Valley, 35km from Los Angeles.
Justin also proved he drives a hard bargain in the sale, talking the price down from $7.5m.
He is expected to move in at the end of June and local residents are keen to welcome him to the area.
Mayor of Calabasas, Mary Sue Maurer, told TMZ: "Justin is welcomed to Calabasas and his privacy will be respected just like everyone else's."
Two security gates
One of the reasons Justin - who is regularly mobbed by screaming fans - bought the house is said to be because it has two security gates.
Justin had been interested in another house - a bachelor pad which Ashton Kutcher had been renting after splitting from wife Demi Moore - but the Two and a Half Men actor decided to act fast and buy it so he could keep it.
Ashton explained: "All of a sudden my assistant tells me there's somebody coming to look at the house to maybe buy it. I get a text from this guy [Justin] and he's in my house, checking it out, trying to buy my house.
"He's like 'Yo, I'm in your house right now. I'm checking it out'. I'm like 'What? Are you trying to take my house from under me?'
"I was like 'I don't want to lose this house'. He forced me to buy a house. He's trying to steal my swagger."
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Scary death threats!
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Fin24 user Asia writes how she managed to rehabilite herself from splurging on feel-good iitems and keep clean from the bondage of lifestyle debt.
JohannesburgCore Candidate (Pty) LtdR500 - R800 Per Year
Cape TownE-Merge IT RecruitmentR25 000 - R30 000 Per Month
Cape TownHire Resolve
TownhousesR 1 800 000
Apartments / FlatsR 3 100 000
HousesR 6 200 000