We investigated latitudinal changes in mesozooplankton community structure during a cruise between October 16 and November 30 of 2007 from four distinctive regions in the northwestern Pacific Ocean: Warm pool area (longitude $135^{circ}$ line), Philippine EEZ (PEEZ), Japan EEZ (JEEZ), and East China Sea (ECS). Major taxa of numerical importance were Clausocalanidae (Clausocalanus spp.), Oncaeidae (Oncaea spp.), and Oithonidae (Oithona spp.) in oligotrophic regions, however Paracalanidae (Paracalanus spp.) was the most abundant group in the ECS. Mesozooplankton size group of <1 mm dominated in PEEZ and WP (48% and 56%, respectively), but mesozooplankton (>1 mm) were of importance in the JEEZ and ECS (34% and 38%, respectively). Mesozooplankton biomass and abundance were high in the JEEZ and ECS, and low in the oligotrophic WP and PEEZ waters, with positive relationship with both total Chl-a and heterotrophic protist biomass. Latitudinal change in mesozooplankton community structure was related with water temperature, with copepods such as Lucicutia spp. and Pleuromamma spp. being present only in warm waters. The geographical expansion of mesozooplankton with a preference for warmer waters could potentially be useful as an indicator for detecting ocean warming.