Czech and English are languages which differ with respect to the implementation of voicing. Unlike in English, there is a considerable agreement between phonological (systemic) and phonetic (actual) voicing in Czech, and, more importantly, the two languages have different strategies for the assimilation of voicing across the word boundary. The present study investigates the voicing in word-final obstruents in Czech speakers of English with the specific aim of ascertaining whether the degree of the speakers’ foreign accent correlates with the way they treat English obstruents in assimilatory contexts. L2 speakers, divided into three groups of varying accentedness, were examined employing categorization and a voicing profile method for establishing the presence/absence of voicing. The results suggest that speakers with a different degree of Czech accent do differ in their realization of voicing in the way predicted by a negative transfer of assimilatory habits from Czech.