This study focused on the multimodal social semiotic analysis of the flagship poster slogans of the national agency in the Philippine government. The semiotic modes and their strategies, multimodal presentation and how do these elements influence the reception and interpretation of their target audiences were described. The research materials were 51 flagship poster slogans from the different national agencies in the Philippine government; 10 participants were also interviewed in In-depth interview and focus group discussion. Results revealed that the analyzed flagship poster slogans utilized semiotic modes specifically linguistic, visual, gestural, and spatial mode along with strategies involved in these modes to showcase their campaigns. Further, representational, interactional, compositional metafunctions of Visual Grammar were employed by the flagship poster slogans to boost the engagement, interpretation, and reception in their target audience. Lastly, the essential themes that emerged from the analysis of the interview regarding the reception and interpretation of multimodal composition of flagship poster slogans were vibrant imagery, familiarity of language, familiarity with concerned agency, arousal of viewers interest, and context dependent impressions; these essential themes are also found to be in connection with the baseline metafunction that were used in the flagship poster slogans of the national agencies in the Philippine government.