The loved-up couple headed to Mick Norcross' popular Sugar Hut nightclub to celebrate the occasion with their co-stars.
Lydia and Arg were seen cosying up to one another on the dancefloor, before sharing a smooch at the party.
Looking blissfully happy, the couple seemed oblivious to all the noise and dancing around them!
Lydia and Arg were joined by Danielle Armstrong, Peter Wicks, Jessica Wright, Tommy Mallet and James 'Lockie' Lock, who went all Kylie Minogue in gold hot pants!
Having recently celebrated their seven-year on-off relationship, Arg and Lydia are now back on track following a recent blip in their romance.
Lydia got upset with Arg for drinking again following his stint in rehab, but after a heart-to-heart he promised he would change for the better.
Arg later said in a video interview: "I've got to make these changes and continue my progress that I've made so far. I've had a few slip ups recently so I've just got to nip it in the bud.
"[I need to] make more effort with Lydia in regards to the relationship and do some nice things, start being more of an adult and more responsible."
TOWIE airs every Wednesday and Sunday at 10pm on ITVBe.
For exclusive competitions and amazing prizes visit Reveal's Facebook page NOW!
10 reasons why we want to be in TOWIE: