Semiconducting polymers have the potential to be used in thermoelectric devices that are lightweight, flexible, and fabricated using solution processing. Because of the structural and energetic disorder of these polymers, the relationship between their structure and thermoelectric properties is complex. We review how interrelated processing routes and doping methods affect the thermoelectric properties of polymers. The studies highlighted here have led to correlations between thermopower and electrical conductivity that can be described by theories under investigation. With greater understanding of the materials properties behind their performance, semiconducting polymers can be used in future power generation or cooling devices.