Despite throwing a massive party on Thursday (1 September), the gorgeous girl made sure to make the most of reaching the milestone age - especially as her actual birthday wasn't until today! We like your style, Kads.
Last night, the reality star headed to celeb-fave Café De Paris for a Saturday night of birthday festivities and luckily for us, she gave us a glimpse of her outfit before heading out.
And if we thought Thursday's outfit, Kady has upped her game even more - if that was possible?!
Her dress choice? A slinky metallic pink number that featured a halterneck top and plunging neckline. Complete with a cut-out front and skort-style hem, we're seriously crushing over this.
Keeping it simple, Kady shunned jewellery and wore some similar metallic-hued barely there sandals that showed off her white pedi.
Meanwhile in the barnet department, the mega babe piled her long brown locks up into a super chic bun and scored high on the make-up marks with killer contour and fluttery lashes.
Boyfriend Scott - who she met on this summer's Love island - couldn't help posting a sweet birthday tribute to his pocket rocket.
Gushing on Instagram, he wrote: "Happy 21st Birthday to this little beauty @kadymcdermott! Can't actually get my head round how young she is when she really does have such a strong and wise little head on those shoulders of hers!
"I don't like to admit it because she drives me absolutely nuts but I've learnt so much from her and I continue to do so every day! This girl knows what she wants in life and trust me she will achieve it! What a journey we've been on together and I hope we have many more adventures to come!"
Continuing, he wrote: "I know I'm hard work so thanks for putting up with me and not giving up on me just yet. Have an amazing night tonight and il see you tomorrow you absolute rocket. Love you lots and lots little pea."
Awww, how cute is that? Talk about couple goals.
No doubt Scott is spoiling her rotten today!