Motivation determines students' success in academic writing. The current study adopted 28 items of the academic writing motivation questionnaire by Payne (2012) translated into Indonesian language to explore students' motivation in academic writing. This study involved 120 prospective Indonesian language teachers at STKIP PGRI Bandar Lampung that were chosen by stratified random sampling technique. The result indicated that items clustered into four factors, namely (1) enjoyment (a = 0.98; s[superscript 2] = 34.96%), (2) self-efficacy (a = 0.91; s[superscript 2] = 17.90%), (3) instrumentality (a = 0.93; s[superscript 2] = 14.44%), and (4) recognition (a = 0.98; s[superscript 2] = 10.65%) with rotated factor loadings varying between 0.546 and 0.984. These results confirmed that the instrument used in this study had excellent validity and reliability. Based on degree of motivation analysis, the enjoyment had the highest contribution to writing motivation, followed by instrumentality, and self-efficacy. Finally, Pearson correlation analysis revealed the significant correlation between enjoyment and self-efficacy.