Among the main causes of low learning achievement in mathematics learning is a delayed behavior to do tasks, commonly called academic procrastination. The objectives of this research are to describe and to explain the causal factors and consequences of academic procrastination in learning mathematics for junior high school students. This research was conducted for more than five months. The research took place at six junior high schools in Madiun Regency. The research approach was a qualitative descriptive. The types of data sources were six mathematics teachers and six students, in-class mathematics learning activities, and documents. The data collection techniques were (1) questionnaire, (2) documentation, (3) passive role observation, and (3) in-depth interviews. The data were analyzed using an interactive model, which was implemented in two stages. They are at the time or during the course of data collection and after the data collection. The results of data analysis show that academic procrastination is caused by several factors. They are assumption that the tasks assigned are not important, too burdensome, and difficult to work, insufficient knowledge, too perfectionist, bad management of learning, lack of self-regulation, stress and fatigue, lack of social support, indiscipline teachers, and inconducive school culture. Academic procrastination, most importantly, leads to low learning achievement.