Learning-oriented assessments have been implemented in the English language classroom to maximize students' ability to acquire a language through their involvement in assessment processes. Nevertheless, empirical studies investigating the oral communication ability of students using learning-oriented assessments remain limited. This study aims to investigate the effects of a learning-oriented assessment on the English oral communication ability of Thai pre-service teachers and to explore their attitudes towards the model. Thus, the study employed a mixed-methods research design. The participants of the study were 60 first-year students divided into two groups: the control group (N = 30) and the experimental group (N = 30) were selected through convenience sampling. The data were collected for 10 weeks using an oral communication test, a questionnaire, and interview questions. The results of the test were analyzed using a paired sample t-test and an independent sample t-test. The results of the questionnaire were analyzed using descriptive statistics. In addition, the qualitative data were analyzed using content analysis. The quantitative results showed positively significant effects on the development of students' oral communication ability in the aspects of range, accuracy, fluency, interaction, coherence, and pronunciation, with a medium effect size. Additionally, the students positively reported the benefits of learning-oriented assessments as being helpful in improving their oral communication ability. Therefore, this study shows that learning-oriented assessments could serve as one of many alternative approaches to developing English oral communication ability.