Mancienne revealed on Saturday he had more than one option upon deciding to quit Chelsea but felt Hamburg - where he will be reunited with former Blues sporting director Frank Arnesen - was the best.
"I think it'll have a great benefit," he said.
"It's a new challenge for me and to play for a big team such as Hamburg and to be playing week in, week out.
"I'm really honoured to go there and really looking forward to the challenge."
Mancienne will become only a handful of English players to have braved a move to one of Europe's top leagues in recent seasons.
He claimed it was a mystery why more of his compatriots had not followed suit.
"To be honest, I don't know," he said.
"I saw it as a massive opportunity to go abroad and to play in the German league, so I'm really excited by it.
"I did have a few other options, but I saw Hamburg as my biggest option."