In this case study, it is aimed at scrutinizing the existence of [a1] diphthongization in Turkish for the borrowed words from Arabic. Seven Turkish and seven English words containing (ail diphthong were read by eight Turkish and eight English native adult speakers who do not have any speech disorders and the sounds of the words were recorded with a quality of 44.100 Hertz, 16 bit resolution and mono channel onto a computer. Formant analyses of Frequencies of the related words were realized with the help of a computer based speech analysis software called CSL (Computerized Speech Lab). In the light of the independent samples t test analyses, it was found that [a1] diphthongization in Turkish has great similarities with the one in English not only from the standpoint of formant shapes but also the numerical data of the frequencies. It can be proposed that in Turkish there is the [a1] diphthong for the words which were borrowed from Arabic.