For Yorkshire Terriers, a harness is strongly preferred over a traditional collar for walking. Yorkies are prone to tracheal collapse, a condition in which the cartilage rings of the windpipe weaken and flatten, and the pressure from a collar pulling against the throat can aggravate or accelerate this condition. A well-fitted harness distributes the force of leash tension across the chest and shoulders rather than concentrating it on the delicate throat. Step-in harnesses and vest-style harnesses both work well for the breed, with the best choice depending on your dog's tolerance for being dressed.
When fitting a harness, you should be able to slide two fingers between the harness and the dog's body at any point. A harness that is too tight will chafe and restrict movement, while one that is too loose allows the dog to back out of it — a real concern with a breed as small and squirmy as a Yorkie. Adjustable harnesses with multiple points of adjustment around the chest and belly offer the most precise fit. Measure your dog's girth regularly, as even small weight changes can affect fit at this scale.
Collars still serve an important purpose even if you use a harness for walking. A lightweight, flat collar is the appropriate place to attach identification tags and rabies vaccination tags. Look for collars with breakaway safety clasps that release under pressure if the collar gets caught on furniture or fencing, preventing strangulation. The collar should sit comfortably around the mid-neck with enough room to fit two fingers beneath it.
Leashes for Yorkshire Terriers should be lightweight and no more than six feet long for everyday walking. A heavy leash designed for a larger breed will weigh down a Yorkie's small frame and make walks uncomfortable. Retractable leashes are generally not recommended for toy breeds because the thin cord can cause friction burns, and the sudden stop at full extension can jerk a small dog off its feet. A standard fixed-length leash gives you consistent control and keeps the dog at a safe, predictable distance.