The super producer was behind the desk for the singer's lead single - taken from his second album 'FutureSex/LoveSounds' - and while he immediately believed in the track, others weren't so sure.
Speaking to the 'Complex's Blueprint' video series, he said: ''I knew it was a feeling. Everybody was like, 'That ain't it.' I said, 'Yes, it is, that's the one' ... The beauty of a hit is not knowing it's a hit but you know it feels good.''
The song went on to top the Billboard Hot 100 chart in the US, while it also became his first Number 1 single in the UK.
The pair first worked together in 2002 on 'Cry Me A River' - from Justin's debut solo LP 'Justified' - and there was a connection with the way they worked on music.
Timbaland added: ''I went in the booth and I knew that sound would move him in a different way. I knew the chemistry that we both had ... like yeah, musically, we on to something.''
On Friday (05.01.18), Justin's new single 'Filthy' will be released, with Timbaland credited as co-producer on the record.
He previously told Rolling Stone magazine: ''The music we just made? It's gonna put him on another plateau.''
Meanwhile JT, 36, is set to drop his first album in four years - titled 'Man of the Woods'- next month, and he's got a star-studded list of collaborators, with the likes of Alicia Keys and Chris Stapleton appearing on the record.