The actor ended the post on a sweet note, writing, "Bring on the cuddles! So much happy right now".
Needless to say the comments section was soon lit up with messages of congratulations for the new uncle.
SAS Australia star Erin McNaught was among the many well wishers, penning, "Too cute! Congrats to the whole fam☺️💗
American actress Michelle Monaghan was also visible in the comments, writing, "Omg!!!! She’s so happy!!".
Lincoln also shared a series of snaps to his Instagram story, including snaps of his nephews beaming down at their new sister.
"Welcome to the world little Sophie. We all love you," the 33-year-old wrote, before apologising for the baby "spam", claiming his new niece "is just too adorable". We couldn't agree more.
The sweet addition to the family is delightful news for the Lewis family after what has been a rough year.
In February, it was revealed that Lincoln's NRL star dad Wally split with his mother Jacqui after 36 years of marriage. The athlete soon after struck up a romance with Townsville mum Lynda Adams.
The former Home & Away actor got candid about the separation on The Anj, Rob & Robbo Show.
“It's been hard on everyone obviously, and anyone who goes through stuff... it's obviously going to be hard,” Lincoln told host Rob Knight of how the family has been coping.
“You're going through things in the public eye and that comes with the territory.”
WATCH: Lincoln Lewis was GHOSTED after pitching Home & Away storyline (Story continues after video)
Asked specifically about how his mother Jacqui was doing, Lincoln shared that she has had a lot of support.
“We've all banded together, we're a tight family unit. She's got some amazing friends around her. That's the thing that gets anyone through,” the Tomorrow When The War Began star replied.
“At the end of the day, to have good people around you that love, care and support you, is the main thing.”
He added: “So obviously she's got that around her. We have our up days and our down days, but she's surrounded by good people.”