There have been at least 12 attempted attacks on religious institutions since a court verdict on New Year's Eve allowed non-Muslims to use the word "Allah" when referring to God.
The ensuing protests and violence have heightened religious tensions in the Muslim-majority nation.
Bakri Zinin, Malaysia's federal criminal investigation chief said police were investigating whether the eight arrested were also linked to the attacks on 10 other churches, which had been pelted with Molotov cocktails, stones and paint.
"Eight people have been arrested and they are believed to be involved in the arson attack on the [Metro Tabernacle] church. They have been remanded for seven days to facilitate investigations," he told reporters on Wednesday.
"We will investigate whether they are also linked to other cases [but] we believe we have solved this case. So please I advise the public, don't do something that will threaten racial and religious harmony."
The three-storey Metro Tabernacle church in Kuala Lumpur was set ablaze on January 8 in a firebombing that left its ground floor destroyed.
Church leaders said witnesses saw four people ride up to the building on motorbikes, smash the church's windows and throw objects into the building.Bakri said the first of the eight to be arrested was detained on Tuesday after seeking hospital treatment for burns on his hands and chest.
The group were all aged between 21 and 26, and included three relatives - two siblings and their uncle. The remainder were friends of the family group.
Last month, the High Court ruled in favour of the Catholic Herald newspaper which has used "Allah" as a translation for "God" in its Malay-language section.
Malaysia's government has said the word should be used only by Muslims.
The court's final ruling on the issue was suspended pending an appeal, after the government argued the decision could cause racial conflict.
Malaysia's population is 60 per cent Muslim ethnic Malay, but also includes indigenous tribes as well as the large ethnic Chinese and Indian communities that practice Buddhism, Christianity and Hinduism, among other faiths.
More than half of Malaysia's Catholics are from indigenous groups, most of whom live in the Borneo island states and who mainly speak Malay.