A quasi-experimental research design was used to determine the effects of a physical activity promotion program on PSE, PA and PF among Thai adolescent girls. The population of the study was Thai adolescent girls in grades seven and eight at two public schools in Chonburi province, Thailand. Inclusion criteria, for the sample, were Thai adolescent girls who were not participating in any athletic programs and whose parents had given consent for them to participate. Potential participants were excluded if they had any illnesses or conditions that would limit physical activity. There were 59 participants in the experimental group and 47 in the control group. To protect participants’ human rights, the study proposal was approved by the researcher’s University Ethical Committee. Parents of the students were given an information sheet explaining the study’s purpose, procedure and benefits. Those parents who allowed their daughter(s) to take part in the study indicated their consent by signing a consent form. Potential adolescent participants were informed about the details of the study and what their participation would entail prior to being asked to sign an assent form to participate.