Confirm your Citizen Eco-Drive model is designed for user battery replacement; many Eco-Drive watches use a rechargeable cell and are not meant to be opened without tools
If the watch has a screw-down or sealed case back, do not attempt replacement without tools
If your model has a snap-on back and a removable battery compartment, open only if it can be done by hand
Remove the watch from your wrist
Place the watch face down on a soft cloth
Locate any hand-openable battery cover or compartment latch
Use your fingernail to gently lift or slide the cover open
Note the battery type and orientation before removing it
Lift the old battery out carefully with your fingernail if accessible
Insert the new battery in the same orientation
Press the battery into place until it sits flat
Close the battery cover or compartment securely by hand
Check that the case back is fully closed and aligned
Reset the time and date if needed
If the watch does not restart, needs a rechargeable cell, or the back will not open by hand, take it to a Citizen service center or jeweler