The rapid growth of o nline social media networks like Faceb ook and Twitter is strongly influencing n ews media to engage with such networks for generating newsworthy content, access ing mass audiences for news consumption and using th e platforms for news distribution. While both media’s complement each other as sources of news and information , they also compete against each other as news repositories and are observed vying for the same audiences. We call this phenomenon the competing - complementarity (C - C) engagement. To investigate the C - C relationship w e use Fidler’s “mediamorphosis” concept to explain the metamorphosis of news media in the online domain . We make two contributio ns to Fidler’s concept by offer ing an additional principle “mass user migration” to address the characteristics of metamorphosis and an additional driver “transcended social engageme nt” t o show the force that propels it. Besides, we also propose four accelerators that influence metamorphosis. Theoretical analysis of news media ’s metamorphosis indicates its affinity to online social media. We apply niche and gratification theories to e xpla in complementarity , and displacement effects on media consumption habits to trace competition b etween both media’s