The concept of 'authenticity' or 'the authentic material' has been a controversial issue during the past 30 years. However, in recent years, more emphasis has been given to a multifaceted model and there has been an attempt to put an end to binary definitions of authenticity. In the present study, five types of input authenticity proposed by Brown and Menasche (2008) were taken into account. This model consists of genuine input authenticity, altered input authenticity, adapted input authenticity, stimulated input authenticity and inauthenticity. In this study, an attempt was made to explore the effect of four out of five types of multifaceted input authenticity model on learning idiomatic expressions of EFL learners. A quasi-experimental research study was conducted and 62 male EFL learners were assigned to four groups and four types of authentic idiomatic materials were prepared and taught to them. A one-way ANOVA was run on the scores obtained from a pre-test (which tested participants' idiomatic expressions understanding) and it did not show any significant difference among the participating groups (F = 0.39, p = .757). During the treatment period, which lasted for two months, three sessions a week, four groups received four types of different idiomatic materials with different types of authenticity. A one-way ANOVA run on the scores of the four groups reached statistical difference (F = 31.31, p = .