Mangrove forests are considered as valuable and unique ecosystems in tropical and subtropical regions which have the richest biological, genetic diversity and service resources and very high adaptability to establish in hard environmental conditions (high salinity, anaerobic soils and flooding). The largest area of these valuable and fragile forests is limited to the just south of Iran especially in Hormozgan province. During frequent visits in 2017 and 2018, it was observed a large number of mangrove trees, located in Khamir port (Hormozgan province), to be attacked and damaged by larvae of a lepidopteran species. In the early studies, sever feeding of larvae on different parts of the canopy was observed. Also, in many attacked trees, branch dryness and general weakness of the trees were observed, indicating the high aggressive behavior of the pest. In order to identify the pest, samples of the various stages of larvae and pupae were collected and transferred to the plant production laboratory of Hormozgan Agricultural and Natural Resources Research and Education Center. To morphological identification, the larvae and pupae were placed in incubator at 26 ± 2 ° C, relative humidity 60% and a photoperiod of 14:10 (L: D) photoperiod till the adults emergence. Furthermore, to confirm the morphological identification, we used molecular technique using DNA barcode. To do so, total genomic DNA of the larvae was extracted using CTAB methods and the Cytochrome Oxidase subunit I (COI) amplified using LCO 1490 primers and HCO 2198 primers. A positive PCR product was directly sequenced, edited and deposited in National Center for Biotechnology Information (NCBI) under MH414968 accession number. Blastn search of the ca. 700 bp of COI gene showed that this sequence shared 99% identity with sequence of Streblote helpsi from family Lasiocampidae. Species identification was confirmed using morphological characteristics as well. This is the first report of S. helpsi damages on Avicennia marina in Iran and most probability worldwide.