Here, we report the assembly of single-walled carbon nanotubes (SWCNTs) into two-dimensional structures and networks in aqueous solution. The assembly of SWCNTs was controlled via side-to-side interactions: we found that changes in the reaction conditions led to changes in the structures obtained. Moreover, by dispersing our SWCNT-based assemblies into a polymer matrix, we found that the mechanical properties of thin films can be modified in relation to the kind of SWCNT assemblies employed.