The present study examined the efficacy of autonomy-supportive teaching during elementary school physical education (PE) in influencing pupils' enjoyment, fear of failure, boredom and effort. A sample of 54 pupils attending fifth and sixth grades comprised the control group (typical instruction; n = 27) and the experimental group (autonomy-supportive instruction; n = 27). Pupils' responses were provided four times during a school trimester on perceived autonomy-support provided by the PE teacher, fulfilment of psychological needs for autonomy, competence and relatedness, behavioural regulations for PE participation, enjoyment, fear of failure, boredom and effort. In the autonomy-support condition, levels of the positive motivational indexes remained relatively stable during the trimester. Motivational deterioration was evident for the control group, and especially during the middle and the end of the trimester. Autonomy-supportive teaching leads to enhanced levels of motivation compared to non-autonomy-supportive teaching that may lead to gradual decline of motivation for PE participation.