The Western Morning News says there is “not sufficient demand” for the format, first launched in June 2014.
At the time, seven new editorial roles were created at the Plymouth-based title in order to accommodate the move to seven-days-a-week.
However, five jobs are now at risk of redundancy following the Sunday edition’s closure.
The process of integrating the LW newspaper group within TM began in December, but it is understood that the decision to close the Sunday title was taken locally.
Editor Bill Martin, pictured, said: “We are sorry to announce the end of the Western Morning News Sunday edition but accept there is not sufficient demand for that format.
“The changes announced today are to ensure the newsrooms are adapting to the continually shifting media landscape.
“There will be an impact on some editorial roles as a result of these changes and we are speaking directly to those affected employees.”
Most WMN staff worked across all seven of its editions but a small number formed part of a specialist Sunday team which included both reporting and production roles.
A Twitter account for the Western Morning News on Sunday was still active as of this morning.