The leader of the Church of England said the Pentecost initiative had been well received and more projects will be planned as a result.
Writing in The Church Times he said: "Messages began pouring in from churches around the country that were making time to pray for the witness of the Church and fresh confidence to share their faith.
"It was not just from one particular tradition or area - every tradition and expression of church was represented."
Churches across England are praying for #ThyKingdomCome this Pentecost - join us! https://t.co/hM1xwcB3dShttps://t.co/Klol2bTKuC
— Thy Kingdom Come (@thykingdom_come) April 26, 2016
Justin Welby said church leaders may have been "surprised" to receive a letter from the Archbishop of York and himself earlier in the year inviting communities to focus on prayers.
He went on to say: "Many churches hosted whole weeks of 24/7 prayer, some for the first time, and many in partnership with others in their deanery.
"Some held prayer days, half-nights of prayer, or novenas of prayer.
"The 'beacon' events in cathedrals were packed, and there is no telling how many individuals played their part with prayer at home.
"We estimate that more than 100,000 Christians joined in about 3000 events and services during those ten days."
He wrote that parishes had reported lasting change after a focus on prayer and that there was a desire for more.
Justin Welby said he was impressed by churches getting involved that they would plan a new programme for next year.
"Christians of every tradition, in whatever context, share many things in common.
"At the core of Thy Kingdom Come is one of the most important: a reliance on God to send the Holy Spirit to empower us as witnesses to the good news."
He concluded saying that Jesus lived for human kind and that: "The Spirit is not given primarily to bless us privately, but so that we can bless the world around us - primarily by witnessing to the life-transforming power of Jesus Christ.
"In 2017, the invitation is going out further and wider to pray together in the run-up to Pentecost.
"Churches across the whole Anglican Communion have been invited.
"In the meantime, the presidents of Churches Together in England have called on their Churches to take part."
