The study examined the enhancement of EFL Thai undergraduates' narrative paragraph writing through extensive reading (ER) and investigated the attitudes of EFL Thai undergraduate students towards ER. Forty-nine non-English major students at a public university in Thailand participated in the study over ten weeks. Two experimental groups were assigned. Twenty-five students were assigned to read graded readers one level beyond their current level of competence (i+1), and the other twenty-four students read graded readers at one level beneath their current level of competence (i-1). Quantitative data were collected through the pre- and post-narrative writing tests. A questionnaire was delivered to both groups after testing the participants. Semi-structured interviews were conducted to get qualitative data. The results revealed that ER improved the writing performance of EFL Thai undergraduates in both i+1 and i-1 groups. However, no significant difference was found between the two experimental groups on overall writing performance and the other five specific writing features including content, organization, vocabulary, language use, and mechanic. Moreover, the results indicated that both i+1 and i-1 groups had positive attitudes towards ER. The findings suggested that ER is an effective method for EFL students to improve their narrative writing performance, and it should be promoted in English classrooms.