The purpose of the study is two-fold. First, a statistical analysis of the morphology of causative/inchoative verb alternation is carried out in Japanese and in 13 Altaic languages, i.e., Turkish, Turkmen, Nanai, Khakas, Udihe, Uzbek, Sakha, Manchu, Kyrgyz, Mongolian, Kazakh, Ewen, and Azerbaijani. The findings reveal that causative/inchoative verb alternation (a) can be realised via the insertion of an infix (‘-uul-’, ‘-e-’, ‘-g-’, etc.); (b) can be inchoative root-based, with transitive verbs derived via attaching a suffix to the inchoative verb roots (‘-dur-’, ‘-t-’, ‘-ir-’, ‘-dyr-’, ‘-wəən-’, ‘-buwəən-’, ‘-r-’, ‘-wənə-’, ‘-nar-’, ‘-ier-’, ‘-er-’, ‘-bu-’, ‘-ʊkan-’); (c) can be causative verb-based, with inchoative verbs being derived via attaching a suffix to the causative verb roots (‘-p-’, ‘-n-’, ‘-ul-’, ‘-il-’); and (d) can be realised via consonant alternation (‘-r-’ (transitive) / ‘-n-’ (intransitive); ‘-t-’ (transitive) / ‘-n-’ (intransitive)). This study further attempts to pin down the affiliation of these languages with the Japanese language. It compares the morphological findings with Japanese bound morphemes in causative/inchoative verb alternation and then delves into the phonological issues, i.e., consonant alternation and vowel harmony. A proposal is put forward: phonologically and morphologically, Japanese has a good deal of resemblance to the 13 Altaic languages.