A laterally placed capacitor package assembly and an assembly method thereof are provided. The laterally placed capacitor package assembly includes a wound capacitor package structure and a capacitor supporting structure. The wound capacitor package structure includes a wound assembly, a conductive assembly and a package assembly. The conductive assembly includes a first conductive pin and a second conductive pin. The capacitor supporting structure includes a supporting portion configured to support the wound capacitor package structure and a plurality of positioning portions extending outward from the supporting portion. When the laterally placed capacitor package assembly is configured to be laterally disposed on a circuit substrate, a first exposed portion of the first conductive pin and a second exposed portion of the second conductive pin can be laterally and electrically connected to the circuit substrate without bending.