Polyphenylsulfone was thermally aged at temperatures corresponding to its processing and was mainly shown to undergo crosslinking as observed by measurements of average molar mass, rheometry and changes in glass transition temperature. Those experiments were completed by mechanical testing thin sample films at 250 and 280 °C. The same degradation mechanisms were observed and result in a strong decrease of ultimate strain accompanied by a slight decrease in elastic modulus and yield stress. Overall results were discussed using well know structure-properties relationships.