The pair, who are reported to be more than just friends, couldn’t hide their excitement as their names were called out by host Tess Daly.
They found themselves screeching enthusiastically before embracing each other for several seconds after hearing the good news.
An elated AJ, 23, scooped Mollie, 30, into his arms and span her around energetically upon hearing that they had secured a place in the semi-finals.
The professional dancer then nuzzled his head into Mollie’s neck as they celebrated being one step closer to lifting the glitter ball trophy.
At one point, the pair stared deeply into each others eyes, smiling at one another while they continued their embrace.
The couple have reportedly got very close after meeting on Strictly Come Dancing a few months ago and immediately hit it off.
Strictly judges have even commented on the duo’s “believable chemistry” and questioned whether they are dating.
Mollie and AJ set tongues wagging when they sat down to discuss moving through to the semi-finals with presenter Claudia Winkleman, 45.
The professional dancer looked very cosy next to the singer as he kept a tight arm around her as they discussed their relationship.
He had mentioned that they had spent more than 300 hours training, before Claudia joked that they had spent “only half that time kissing”.
Appearing embarrassed Mollie began to playfully slap Claudia as her fellow dancers gasped.
Mollie will be competing against Joe McFadden, Mollie King, Gemma Atkinson and Debbie McGee in the semi-finals next week.
Strictly Come Dancing continues Saturday at 6.45pm on BBC One.