[Objectives]  To describe morphological characteristics that can be used to accurately identify the moth Spodoptera frugiperda, an invasive pest that has recently become established in China. [Methods]  Stable, diagnostic, morphological characteristics of male and female moths, including male genitalia and female bursa copulatrix are described. [Results]  Body size and other 20 morphological characteristics are too variable among individuals to be used to accurately identify S. frugiperda. In addition to 4 forewing characteristics, including black spots on the base of the forewing, 6 other morphological features, such as black scale bands on the labial palp, are found to be sufficiently invariant among individuals to serve as diagnostic features. An oblique orbicular spot in the middle of the forewing, and other 3 morphological characteristics are confined to males and females. The uniform color of humeral plates and 4 other features are confined to males, whereas the characteristic “same color of the inner part to the forewings” is confined to females. Four and two newly identified external morphological features accurately distinguish S. frugiperda from S. litura and S. exigua moths, respectively. Newly identified 6 diagnostic features of male S. frugiperda genitalia include juxta longer than wide, whereas newly identified 4 features of females bursa copulatrix include the base of the ductus bursae being obviously wider than the end. Three features of the male genitalia, and 3 of the female bursa copulatrix, accurately distinguish S. frugiperda from male S. litura and female S. exigua, respectively. [Conclusion]  The results of this study not only provide morphological characteristics of the forewing but also additional morphological characteristics of other body part that allow the accurate identification of male S. frugiperda. Forewing features that allow the accurate identification of females are also provided for the first time. In addition, our results provide a useful reference on the genitalia of noctuids, including some newly described features of the male genitalia and female bursa copulatrix.