The church and a neighbouring hall have a combined floor area of 560sqm and sits on 1012sqm of land and an organisation called Miramar Peninsula Community Trust will lease the church from Jackson.
Built in 1932, in the Romanesque Revival style, the church was designed by William Fielding, who was also responsible for Wellington's Congregational Church in Cambridge Tce (1916), the Evening Post building in Willis St (1927), and the Methodist Church in Waitoa Rd, Hataitai (1928).
The separate hall dates back to 1913.
Both require earthquake strengthening and have a heritage classification under the Wellington district plan.
Enterprise Miramar Peninsula chair Thomas Wutzler said St Christopher's was one of Seatoun's iconic buildings.
This is not the first time Walsh and Jackson have saved a church's bacon. In 2007 they bought the Our Lady Star of the Sea Convent Chapel, built in 1924, which is perched on the hillside overlooking Seatoun.
The church had been closed in 2002 due to earthquake concerns.
By 2014, the refurbished church had so much new steel and concrete that it was up to 100 per cent of the building code.
In 2011 the Jacksons bought Wellington's BATS theatre, and undertook earthquake strengthening.
Jackson ranks 14th on the National Business Review's rich list, and is said to be worth $630m.