Churches are opening their doors for people to meet and pray across the whole area in solidarity with the Gross family. Leaders have also been prayer-walking in the area.
The specific churches that will open can be found on the "Find Alice Gross" Facebook page. The prayer event launches at 7:30pm on Sunday.
Linda Ward from Bless Church Ealing helped set up the gathering and told Premier's News Hour: "What the Church should be doing...[is being] involved with our communities, and of course wanting to bring a sense of hope where there is despair.
"First and foremost our prayers obviously are for the family at this tragic time. One cannot comprehend what they must be going through.
"Having a positive focus, a way in which comfort can be found at such an awful time, is so essential. So the Church has a critical role to play."
Alice Gross, 14, was found in the River Brent in her hometown of Hanwell, West London, on Tuesday.
A 41-year-old Latvian builder, Arnis Zalkalns, remains the prime suspect after being seen on CCTV cameras fifteen minutes after Alice was last seen.
Zalkalns has been missing for more than a month.