The purposes of this study were to examine the quality of summary writing and type of problems made by Thai EFL English major students and also elicit opinions regarding problems encountered by these EFL learners in summary writing. 67 pieces of summaries written by fourth year English major students who enrolled in a research report writing course (205426) in the first semester of academic year 2021 at Naresuan University were collected and analyzed. It was found that the quality of summary writing produced by these EFL writers was viewed as "fair", and there were no significant differences among all dimensions. They were all regarded as "fair". Each dimension revealed the main problems mostly encountered. Concerning their opinions about summary writing problems, they thought that they found it difficult to find the main ideas of the text and finally lost focus. In addition, having difficulty in choosing vocabulary to replace the words from the original source when paraphrasing and having little time for revising were also their main problems. Pedagogical implications for L2 learning and teaching summary writing are discussed.