Spodoptera frugiperda has been reported in China since the beginning of 2019, threatening maize production and raising questions about interactions with indigenous pests on maize. Spodoptera frugiperda is in the same feeding guild as the indigenous species Ostrinia furnacalis, with both pests attacking maize plant tissues such as whorls and tassels. In this study, the interaction of these species was assessed under laboratory and field conditions by examining the survival and predation rate of larvae in maize whorls and tassels. Intraspecific and interspecific interactions of larvae were assessed to characterize movements in arenas in the presence and absence of food. When S. frugiperda and O. furnacalis were present at an equal ratio, S. frugiperda prevailed over O. furnacalis with a high survival rate (over 90%) and predation rate of O. furnacalis (over 40%) under most scenarios in both laboratory and field conditions. When both species occurred at different ratios in the field, S. frugiperda had on average almost 16 times the number of survivors as O. furnacalis on whorls, and 8.3 times the number on tassels, highlighting a substantial advantage in these environments. Spodoptera frugiperda larvae undertook a low frequency of lethal attacks (strikes) and showed a higher incidence of defensive movements compared to O. furnacalis. A field survey showed that S. frugiperda larvae can colonize vegetative plant stages in maize, but it remains to be seen if competitive interactions can be linked to population dynamics of both species though they are expected to favor S. frugiperda.