According to the 16th century ethno historical documents, Guarani pottery decoration and formal variability were related to distinct kinds of vessel's use and painted pottery was used mainly in ritual situations. We analyze archaeological pottery collections from Rio Grande do Sul North shore and Norwest region, seeking to explore the relationship between graphic patterns and distinct functional types of vessels, as well the regional and/or chronological stylistic variation of the sample. In the case study here presented, we suggest that painted pottery has high potential for the analysis of issues related to pre-colonial Guarani alterity and their social cosmological universe.