Functional Data Analysis (FDA) is used to investigate Tone 3 sandhi in Taiwan Mandarin. Tone 3 sandhi is a tone change phenomenon that arises when two low tones occur in succession resulting in the first tone being realised as a rising tone. Tone dyads T2T3 and T3T3 were compared in terms of their F0 contours and velocity profiles. No difference was found between the F0 contours of the two tone dyads. In contrast, velocity profiles showed an increased difference in the later part of the seemingly similar rising movements of T2 and sandhi T3, with a steeper rising-falling movement in the former than the latter. This research demonstrates that FDA can elucidate more detail in the time dimension than that of conventional techniques commonly employed in the current phonetic literature.