Fill a bucket with 1 to 2 tsp. mild dish soap and 1 gallon warm water.
Pull the leather couch away from the wall and remove any pillows or cushions if necessary.
Dip a lint-free cloth in the soapy water and wring it out. Wipe the leather couch, starting from the top and working your way down. Rinse the cloth in the bucket as often as necessary. Clean the sides and back of the couch, finishing with the cushions.
Empty the bucket of soapy water and refill it with clean water. Dip a clean cloth in the bucket and wring it out. Wipe away any soapy residue from the leather couch and cushions with the cloth.
Dry the leather couch and cushions with a towel.
Apply leather protectant to a clean, lint-free cloth according to the manufacturer's instructions. Apply a thin layer of protectant to the leather couch and cushions, wiping away any excess with a clean section of the cloth.
Push the couch back to its original position and replace the cushions.