Lowe told Digital Spy that Grimshaw, who took over from Chris Moyles earlier this week, is a "natural broadcaster" which is what listeners need in the morning.
"He's killing it, man. He's doing a great job. Smart money would be on me saying that, right? But I'm not gonna lie to you," he said.
"I think Nick has done incredible taking over that job with the pressure he's under, given Chris Moyles has broken countless records in that position; some records which will never get beaten."
Over half of readers (55.3%) who voted in Digital Spy's exclusive poll revealed they were unimpressed with Grimshaw's debut show, with 17.1% saying it had promise and 27.6% not wanting to form an opinion so soon.
Lowe continued: "Up to Nick taking over, Moyles is the best who ever did it. And Nick has a chance to be his own man and create his own legacy in that role.
"The first few days are terrifying in any new job, let alone the biggest gig in music radio."
Of Grimshaw's well-known friendships with celebrities, Lowe added: "It's great that Nick is mates with the artists that the audience really like.
"He can reach out and get Harry Styles or Rita Ora on the phone because he knows them, and that's what the audience want: to feel that DJs are the most respected conduit between them and their favourite artist."
Watch Digital Spy's interview Nick Grimshaw below:
Nick Grimshaw's career and celeb pals in pictures:
Copyright: Rex Features Beretta/Sims/Rex Features