While a growing body of research investigates the influence of orthographic input on the acquisition of second language (L2) segmental contrasts, few studies have examined its influence on the acquisition of L2 phonological processes. Hayes-Harb, Brown, and Smith (2018) showed that exposure to words’ written forms caused native English speakers to misremember the voicing of final obstruents in German-like words exemplifying voicing neutralization. However, they did not examine participants’ acquisition of the final devoicing process. To address this gap, we conducted two experiments wherein native English speakers (assigned to Orthography or No Orthography groups) learned German-like words in suffixed and unsuffixed forms, and later completed a picture naming test. Experiment 1 investigated learners’ knowledge of the surface voicing of obstruents in both final and nonfinal position, and revealed that while all participants produced underlyingly voiced obstruents as voiceless more often in final than nonfinal position, the difference was only significant for No Orthography participants. Experiment 2 investigated participants’ ability to apply the devoicing process to new words, and provided no evidence of generalization. Together these findings shed light on the acquisition of final devoicing by naïve adult learners, as well as the influence of orthographic input in the acquisition of a phonological alternation.