This research investigated language learning strategies used in English writing by 100 Thai undergraduate students. It analyzed differences in the use of language learning strategies in English writing in the second semester of the 2019 academic year at Kasetsart University in Chonburi, Thailand. The research instrument was a 50-item questionnaire adapted from Oxford's strategy inventory for language learning (SILL). Data on language learning strategies used in English writing were examined using descriptive statistics (mean, frequency, percentage and standard deviation). Differences in the use of language learning strategies in English writing were analyzed by t-test and F-test. The results indicated that primarily, students used social strategies, followed by memory strategies, compensatory strategies, metacognitive strategies, cognitive strategies and affective strategies in English writing, respectively. Significant differences in the use of language learning strategies in English writing were found on students' field of study, year of study and writing frequency, except gender, age and English point.