Deviations are one of the ways that poets and writers apply to make the language effective. In the contemporary Iranian poetry, along with the innovation movements led by Nima Yooshij, poets went beyond the measured language and made some changes in the rules that dominated the language. The use of poets' unorthodox language has led to lexical, semantic, morphological, syntactic and orthographical deviations in their poems. Many deviations are seen in the poems of the poets who pioneered the development of contemporary Iranian poetry and accepted important representatives. In this article, after giving information about the development of contemporary Iranian poetry, the types of deviations in poems written by prominent poets have been identied and sampled, and the effects of these deviations on their poems have been evaluated. The deviations we encountered in the poems were examined under semantic/unusual connotations, morphological, syntactic and orthographical deviations.