Vanessa Bryant revealed she discovered the sweet note - addressed to the "Love of my Life" - four months after she lost both her partner and their daughter Gianna in a helicopter crash in Calabasas, California.
Sharing a photo of the envelope on Instagram, she wrote: "Yesterday I found an envelope labeled To: The Love of my Life.
"From, Tu Papi I waited to open one more letter on my birthday. It gave me something to look forward to today. (sic)"
Vanessa - who turned 38 on Tuesday (05.05.20) - also has Natalia, 17, Bianka, three, and Capri, nine months, with Kobe, and she added how "grateful" she is for their three daughters during such tough times.
She continued: "Missing the Love of my Life and my sweet little Mamacita- my fellow Taurus.
"Grateful to wake up to my 3 sweet girls today. Wish we were all together. (sic)"
Khloe Kardashian responded to the touching social media post, wishing Vanessa all the best and adding that the note "is a sign he's with you".
She commented: "Happy birthday V! This is beautiful! You deserve this so much!
"I pray you know how loved you are today and everyday! This is a sign he's with you. I'm praying for you always! I love you"
On Friday (01.05.20), Vanessa paid tribute to her late daughter Gianna on what would have been her 14th birthday.
Alongside a photo of her girl, she wrote: "Happy 14th Birthday to my sweet baby girl, Gianna. Mommy loves you more than I can ever show you. You are part of MY SOUL forever. I miss you so much everyday. I wish I could wake up and have you here with me. I miss your smile, your hugs and your giggles. I miss EVERYTHING about YOU, Gigi. I LOVE YOU so much!!!!!!! (sic)"