WASHINGTON—Google has barred high-interest consumer loan services from its app store, limiting payday lenders’ access to customers.

The Alphabet Inc. unit recently prohibited apps from offering personal loans with an annual percentage rate of 36% or higher on its Google Play app store. The move inserted the technology giant into a fight over payday loans, which often carry triple-digit interest rates. The shift was implemented in August with an update to Google’s app-development guidelines for the Android operating system,...