More than 700 people walked from the Bryn-y-Gog estate where April was abducted on Monday to St Peter's Church at the centre of the mid-Wales market town.
Many wore pink ribbons to show their hope that she will be found alive.
At the church service Reverend Kathleen Rogers offered prayers for April's parents.
"Coral and Paul may not be with us this morning but we hold them very close in our hearts as we pray for them," she said.
Former lifeguard Mark Bridger was charged on Saturday with abducting and murdering April.
He is also accused of perverting the course of justice and will appear before Aberystwyth Magistrates' Court tomorrow.
Superintendent Ian John said police were still searching for April with the same "rigour that we've had since day one."
Machynlleth Mayor Gareth Jones said: "It's extremely important that there's support in place for everybody, obviously April and her family and the general community at large as well.
"There's still hope for April."