Although Ilocos Norte has some Roman Catholic, several other religious sects have a strong following in this area. Of these, the most notable is the Aglipayan Church, founded by Batac City native Gregorio Aglipay.

Ilocos Norte is home to several famous Roman Catholic churches:

Paoay Church (St. Agustine Church) - named a UNESCO World Heritage Site in 1993.

St. William's Cathedral in Laoag - famous for its Sinking Bell Tower, found 85 meters away.

St. Monica Church in Sarrat - biggest church in the Ilocos Region.

Bacarra Church - destroyed during an intensity 7.8 earthquake in 1983, reconstructed and reinaugurated in 1984.