The prosodic features in reading aloud assignment has been associated with the students' decoding skill. The goal of the present study is to determine the reliability of prosody for assessing reading fluency of adult ESL students in Indonesia context. The participants were all Indonesian natives, undergraduate students, adult females and males who have learned English in school (at the very least twice a week) for more than 12 years. Text reading prosody was assessed by reading aloud task and the students' speaking manner was taped and measured by using the Multidimensional Fluency Scale, as for text comprehension was assessed with a standardized test. It was discovered by the current study that prosody is a reliable sign to determine reading fluency and also reading comprehension. The student who did not read the text prosodically (with appropriate expression) actually showed that he/she failed to comprehend the text. This study also revealed that a struggling reader was also having low comprehension capacity in listening spoken texts. The ESL students' common problems to acquire prosodic reading skill are low exposure to the target language and do not have a good model to imitate prosodic reading.