Faulty Gasket.
The
main reason for condensation in your refrigerator is a defective
gasket. The rubber seal around the door is responsible for keeping
out warm air, but it is prone wearing out. To test if yours is
operating effectively, close your refrigerator door on a dollar
bill. If you can easily move the dollar up and down or remove it,
you should replace your gasket immediately.

Clogged Drain
Pipe. A
clogged drain pipe doesn’t necessarily cause condensation, but it
can lead to the pooling water at the bottom of your refrigerator,
which can easily be mistaken for condensation. If this tube is
clogged by ice, you can melt it with a little bit of hot water or a
well-placed hair dryer. If something else is causing the blockage,
try using a toothpick or drinking straw to dislodge the debris.

Hot Food. Placing
food in the refrigerator immediately after it is done cooking could
be the source of your condensation. If your hot food is stored in
Tupperware with a lid, condensation is sure to form within the
container. Placing hot food in the fridge also raises the
appliance’s internal temperature, making it work harder to keep cool
and increasing your energy consumption.