Ethylene diamine is a colorless liquid, which is strongly alkaline and quite corrosive. It has an ammonia-like smell and is miscible with water in all proportions. When it is mixed with water, then the liquid heats up considerably.

In coordination chemistry, this compound is used as a ligand and it coordinates to many transition metals as a bidentate ligand, where both amine-ends connect to the metal atom.

The pure compound fumes very strongly when it comes in contact with humid air. This is due to formation of a hydrated compound, which has a higher boiling point than the pure compound.

The vapor of ethylene diamine reacts with water from the air. Both compounds are present as vapor and hence are invisible. The reaction product has a much higher boiling point and condenses into many small droplets. A side reaction is absorption of carbon dioxide, which leads to formation of solid ethylene diamine carbonate. This adds to the fumes as smoke.