This study investigates plural formation in Argentine Hunsrück German, a moribund heritage language spoken in Misiones, Argentina. The authors use the Wug test to elicit plural forms from the heritage speakers. A comparison of Argentine Hunsrück German with varieties spoken in Brazil and Germany identifies innovations and retentions in the patterns of plural formation. While previous research shows that plural markers are often lost in heritage language (e.g., Polinsky, 2018), the current study finds variation in plural formation with most speakers retaining a reduced, yet rich plural allomorphy comparable to other varieties of Hunsrück German.