This study examined the relationship between negative pragmatic transfer and language proficiency with reference to the refusal speech acts as realized by Yemeni learners of English as a Foreign Language (henceforth referred to as YLEs). Forty Yemeni learners of English (20 of low proficiency level and 20 of high proficiency level) and 2 baseline groups (20 native speakers of American English and 20 native speakers of Arabic) participated in this study. The data were collected using a Discourse Completion Task (DCT) which consisted of twelve scenarios employed to elicit refusals, namely,three offers, three suggestions, three request sand three invitations. Collecting these three sets of data made it possible to determine the extent to which YLEs' performance differs from native-speaker performance and whether the differences that exist are traceable to transfer from L1. The TOEFL proficiency test was used to determine the proficiency level of Yemeni learners of English. The findings of the study clearly revealed that there was evidence of negative pragmatic transfer from L1 especially with regard to the overall frequency and order of some semantic formulas used. However, the findings of the study indicated that both Yemeni learner groups showed evidence of pragmatic transfer; low proficient learners showed a greater tendency towards L1 pragmatic norms than their high proficient learners.