Army bomb officers were called to examine suspicious objects in the Waterside on Thursday.
At about 10:25 GMT, police discovered what turned out to be a pipe bomb in the front garden of a home in Trafalgar Court.
A second bomb was discovered at Jeffrey Avenue, also in the Waterside area of Derry.
Army bomb experts were at the scene of both alerts.
Area Commander for Derry, Chf Insp Tony Callaghan, said: "Two viable devices have now been recovered for forensic examination and all cordons have been lifted.
"Residents who were evacuated earlier are now returning home. I would like to take this opportunity to thank them for their co-operation and understanding."
DUP councillor Drew Thompson said up to 20 homes had been evacuated at Trafalgar Court.
Community centres were opened for those who had to leave their homes.
Two pipe bombs have been found in separate security alerts in Londonderry.