Originally from Burnie in Tasmania, Weller moved to Gold Coast in Queensland at age 15 (2011) with his family, when his brother Maverick was playing for the Gold Coast Football Club.

Lachie then joined the Gold Coast Suns Academy, but did not qualify as a priority selection due to not fulfilling the length of residence requirements.

[1] During this time, he completed his schooling commitments at All Saints Anglican School on the Gold Coast and played junior football for Broadbeach as well as Southport.

[3] After playing well for Peel Thunder Football Club in the West Australian Football League, Weller made his debut in round 18 of the 2015 AFL season against Greater Western Sydney.

[4] At the conclusion of the 2017 AFL season, after playing 47 games for Fremantle, Weller requested a trade to Gold Coast, subsequently being traded, along with pick 41 in the 2017 AFL draft for pick 2.