Spurs are third in the Premier League and are on course for qualifying for the Champions League.
Defoe insisted that the team spirit under Andre Villas-Boas is a key factor in the side's 12-game unbeaten run.
"I've been here for many years now and in my opinion, in terms of team spirit, this is the best it has been," stated Defoe. "The buzz around the training ground is fantastic. Everyone is putting their work in and even the players who are injured are working really hard to get back.
"That winning mentality we have got now helps us to keep going when things are not going our way. That is a good thing to have.
"I have to say I think this is the best squad since I've been here."
Defoe has made over 300 appearances during two spells at White Hart Lane.