There have been numerous studies to develop eco-friendly concrete. An attempt to reduce the amount of cement used in manufacturing concrete is suggested as one of the solutions for developing eco-friendly concrete. To reduce the amount of cement used in concrete, the pozzolan-reaction materials such as ground granulated blast furnace slag, fly ash, and metakaolin are widely used as the mineral admixture. Red clay deposited broadly in Korean soil is a well known eco-friendly material. Also, activated red clay for increasing pozzolan-reaction can be practically used as a mineral admixture of concrete. Meanwhile, PET fiber made of recycled PET bottle is a type of recycled material and can control micro-cracks in concrete. However, presently, the studies about concrete mixed with recycled PET fiber are insufficient. Moreover, the researches on PET fiber mixed with red clay have been rarely conducted. In this study, drying shrinkage and flexural behaviour of recycled PET fiber added red clay concrete are carried out. To measure drying shrinkage, free shrinkage tests and restrained shrinkage cracking test were performed. To measure flexural behaviour, flexural strength test of reinforced concrete beam was performed. Test results showed that the drying shrinkage is controlled by red clay admixture and PET fiber. Flexural strength of reinforced concrete increased approximately 10% from adding red clay and increased approximately 30% from mixing PET fiber. And, because of reinforcing effect of PET fiber, the ductility of PET fiber added red clay concrete beam increased approximately 3 folds compared to reinforced slag concrete beam.