Studies on washback of not only international standardized proficiency tests, but also localized high-stakes tests have been increasingly attracting considerable interest. The current study explores the washback effects of a Vietnam-made localized English proficiency test named "Vietnamese Standardized Test of English Proficiency, level 3-5" (VSTEP.3-5) on undergraduate students' learning strategies. This research employed a mixed-methods design featuring two major research instruments labeled as questionnaires and semi-structured interviews. Quantitative data were collected from the survey questionnaires delivered to 600 English-majored sophomores at a public university in Central Vietnam. Additionally, qualitative data were obtained and analyzed from semi-structured interviews with 12 student participants through a prudent coding process. The findings indicated that a majority of undergraduate students claimed that VSTEP.3-5 affected their learning strategies in a positive way, especially "cognitive and metacognitive strategies". Besides, preferences for distinct strategies utilized in specific English skills were particularly evident in such productive skills as Speaking and Writing.