Communication between vascular plants through volatile organic compounds (VOCs) impacts on ecosystem functioning. However, nothing is known about that between non-vascular plants. To investigate plant-plant VOCs interaction in bryophytes we exposed rare peatland moss Hamatocaulis vernicosus to VOCs of its common competitor Sphagnum flexuosum in an air-flow system of connected containers under artificial light, supplemented or unsupplemented by far-red (FR) light. When exposed to VOCs of S. flexuosum, shoots of H. vernicosus elongated and emitted six times higher amounts of a compound chemically related to β-cyclocitral, which is employed in stress signalling and allelopathy in vascular plants. The VOCs emission was affected similarly by FR light addition, possibly simulating competition stress. This is the first evidence of plant-plant VOCs interaction in non-vascular plants, analogous to that in vascular plants. The findings open new possibilities for understanding the language and evolution of communication in land plants.