The True Chronicle History of King Leir and his three daughters, anonymously published in 1605, has twice been ascribed to Thomas Kyd: by William Wells (1939) and by Paul Rubow (1948), but without acceptance. Their evidence consisted of the many close parallels in phraseology it shares with Kyd’s accepted canon. This essay seeks to confirm that attribution, using two independent approaches. The first examines its dramatic structure and characterization, using The Spanish Tragedy, Kyd’s most carefully constructed play, for comparison. I show that it contains three features that recur in King Leir: an intriguer who hires an assassin who will be killed once he has fulfilled his contract; the use of comedy in a context involving imminent death; and a vengeful woman, ready for violent action in her own interest. The second approach is through the play’s language, starting with the shared phraseology identified by Wells and Rubow. But where they relied on their memory to detect parallels, I use anti-plagiarism software, which gives complete, objective, and replicable results. Then I study three aspects of the verse in both plays, their use of feminine endings, pause patterns, and idiosyncratic rhyme forms. Both approaches confirm Kyd’s authorship.