Tasks have been given an ever-increasing attention on the part of researchers in the recent decades, particularly in relation to second language acquisition research. A highly influential factor in task performance, motivation, seems to have been neglected by educational researchers, and this negligence toward the role of motivation gets more prominence while considering the part played by motivational changes during task-supported instruction. Informed by this alleged gap in studies on the role of motivation on task performance, the researchers in the current study strived to probe the dynamic character of foreign language motivation during task-supported language instruction both within single lessons and sequences of lessons over a period of six weeks. Having chosen a sample of 7 young adults, the researchers gathered the data by means of: (1) detailed lesson plans, (2) interviews with selected participants conducted after each session during the study, and (3) Motometers filled out at five-minute intervals during a single class to gain information on motivational changes. The quantitative and qualitative analysis of data revealed that language learning motivation changed not only during a single lesson but also from one lesson to the next. Factors responsible for such changes were found to be related to task features, task implementation, and individual differences. The implications of findings are discussed throughout the paper.