The decisions follow appeals from users to remove an Instagram account used by Core Issues Trust, a UK-based promoter of conversion therapy.
"We don't allow attacks against people based on sexual orientation or gender identity and are updating our policies to ban the promotion of conversion therapy services," Tara Hopkins, Instagram's public policy director for Europe, the Middle East and Africa, said in a statement.
"We have removed violating content from @coreissuestrusttv. We are always reviewing our policies and will continue to consult with experts and people with personal experiences to inform our approach," she added.
The platform will also stop recommending content related to conversion therapy, such as testimonials to its efficacy or posts in praise of or in support of the practice, except those in a legislative context.
Earlier this year, Instagram banned advertisements for the process.
A Twitter spokesperson said their platform already enforces against content that promotes conversion therapy under their wishes of harm rule, and is "working to make the training decks more clear so that team members have a wide variety of examples to refer to and our enforcement of this is consistent and scaleable globally."
In the United Kingdom, a total ban promised by Theresa May in mid-2018 has yet to materialize, and has not been included in either of Prime Minister Boris Johnson's legislative agendas set out at the state opening of parliament.