This study investigates the adaptation of word prosody in loanword phonology. First, it explicates several influential loanword theories and reviews some representative cases of prosodic adaptation from different languages. Then, it turns to the focus on the prosodic adaptation of Japanese borrowings into Taiwanese Southern Min (TSM or Taiwanese). TSM is a tonal language typically described as having seven tones and involving a complicated tone sandhi system, whereas Japanese is a pitch accent language with only two different pitches in the standard variety. From the observations on the current corpus, this study demonstrates that Japanese pitch accent of specific words is ignored in the adaptation, but a pattern reflecting a pitch accent system is revealed in the borrowed forms, given that these Japanese loanwords are assigned tone by a default tonal pattern. The default tonal pattern is analyzed under the framework of Optimality Theory. This dissertation also investigates whether tone sandhi applies to Japanese loanwords in the appropriate phrasal contexts. This is an interesting issue because TSM native words have a one-morpheme-per-syllable tendency while Japanese loanwords consist of polysyllabic monomorphemic words. One may wonder if tone sandhi would occur with loanwords in appropriate phrasal contexts, and if so, how tone sandhi in the loanwords is realized. The results of this research illustrate that loanwords can both trigger and undergo tone sandhi. Interestingly, it is observed that both the (rare) native and borrowed polysyllabic monomorphemic words reveal a similar pattern in that tone sandhi only operates on the final syllable but not on non-final syllables, which is consistent with the understanding of TSM tone sandhi as being sensitive to syntactic structure and lexical government. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]