The centre-back endured a frustrating spell under the stewardship of interim-manager Rafael Benitez last season, often finding himself on the periphery of the first team and started just 11 Premier League matches.
However, Terry has been rejuvenated since Mourinho returned for his second spell in charge at Stamford Bridge in the close-season and has been an ever-present in the starting XI in the top flight this term.
And the 33-year-old credits Mourinho for helping him to rediscover his confidence.
"The manager was straight with me from day one," he told Chelsea's official magazine. "When Jose came in, after the first week he said, 'for me, nothing has changed. You're still top, you can still work and play at the top'.
"He showed faith in me, and to get that arm around you is something everyone needs, even if you are one of the more experienced players in the team.
"At the time the manager spoke about it, I think I needed it and, when I got that from him, it not only made me feel 10-feet tall, but it made me want to work even harder for the man in charge.
"It makes you go to that extra level - and I would give everything for the manager."
Chelsea are currently third in the Premier League table just two points adrift of table-toppers Arsenal and Terry believes the side have yet to hit full stride as the club bid to capture the title for the first time 2010.
He added: "It is important that we kick on now, because everybody feels we have another gear to go to.
"I feel as though we have played well in spells, but we have certainly got another level that we can go to and, if we do that, hopefully we can start to pull away from teams."
