The superproducer has worked with Gwen for years and he was there to support the No Doubt frontwoman after her 13-year marriage to British rocker Gavin Rossdale fell apart last summer (15).
The mother-of-three bounced back from the shock divorce by embarking on a romance with country star Blake, a fellow mentor on U.S. talent show The Voice.
They went public with the relationship in November (15) and made their red carpet debut as a couple at the Vanity Fair Oscars afterparty on Sunday (28Feb16), and mutual friend Pharrell, who is also part of the team on The Voice, insists their developing love story is a "beautiful" thing to watch unfold.
"It is popping off!" he smiled to U.S. breakfast show Today. "And it's so beautiful because being there, I watched the both of them go through a lot (with their divorces), and you hate to see your friends go through something so heavy.
"It's kinda (crazy), it's like a miracle, man, just watching that (their new romance develop)."
However, Pharrell admits he was taken by surprise when he first learned Gwen and Blake were a couple, because he had never noticed their chemistry before.
"I had no idea!" he exclaimed. "Then Blake sends me a text message (notifying me) and I'm like, 'Woah!' Never in a million years! You'd never guess it!"
Gwen previously credited Pharrell and Blake with helping her deal with the breakdown of her marriage, but she also confessed she had "never heard" of the Honey Bee hitmaker before joining The Voice in 2014.
"I didn't even know who he was before I was on the show," she laughed to U.S. talk show host Ellen DeGeneres in November (15). "Before I was on The Voice I'd never heard of him before... I'm an O.C. (Orange County, California) girl! Like, what would I know?"
Blake announced his separation and divorce from fellow singer Miranda Lambert in July (15) after four years of marriage, but that reportedly hasn't stopped him or Gwen from considering heading down the aisle again.
"For now, they seem happy with their relationship, but Blake is old-fashioned and a future engagement seems very possible," a friend of the blonde beauty told People magazine this week (begs29Feb16). "Gwen thinks of Blake as the biggest blessing."