who is the smallest dog in the world?
Tiny Chihuahua Milly is the worldâs smallest dog at just 3.8 inches high. 1  Micro Mutt weighs was born in December 2011 but has failed to grow any larger than an average Chihuahua puppy.  She replaces former record holder Boo Boo from Kentucky in the U.S. who towers over her at 4.2 inches.