On leash, dogs enjoy being tethered together, provided they can detect directional changes in their partner's movements. The dog coupler includes a semi-rigid hollow tube, each distal end of which is pressure fitted with a clip fastenable to a dog's collar or harness. Fabricated of resilient plastic tubing, about 18 inches long, the tube, when relaxed, forms a shallow arch. Arched more deeply by compression or, alternately, straightened out, the tube acts like a weak spring but exhibits substantially stronger spring tension when stretched. Because of the tube's three distinct spring constants, two dogs, individually tethered at the tube's distal ends, can communicate, via tube, their relative positions as they move toward or apart from each other. Working to prevent negative feedback, each dog is trained to space itself properly instead of bumping into or pulling away from its partner, thus enabling the two dogs to walk or run well tethered together.