Various languages are used in Tanzanian linguistic landscape. In addition to others, Kiswahili and English are the main languages that are dominant in terms of usage. Sometimes, these two languages are code-mixed on various linguistic levels, such as on morphemes, words, and sentences. However, language relationship, particularly in the context of written texts, does not end at linguistic levels only. Appearance of writings can also give various relationship information between one language and the other. The main objective of this study was to explore how Kiswahili and English languages relate on the context of linguistic landscape using linguistic features such as morphemes, words, and sentences; and non-linguistic features such as language arrangement within texts, colour usage, and font size. Data which has been used to explore relationship of the two languages were commercial advertisements, which used both Kiswahili and English language around Mlimani City area in Dar es Salaam. Data was analyzed using multimodality approach as proposed by Sebba (2012). Sebba proposes the approach to be used to analyze written texts, particularly those from the multilingual societies. The main argument of the approach is that writings appearance can yield a variety of sociolinguistic information, which cannot be obtained in the spoken texts. Thus, Sebba stresses that analysis of the written texts, particularly those found on language landscapes should include both linguistic features and the appearance of the relevant texts. Results of this study show that Kiswahili and English languages complemented each other content wise on the linguistic landscape within the area of study. Further, other features, such as language arrangement, the use of font size, upper and lower cases, and colour made Kiswahili language more dominant and powerful on the commercial advertisement than English language.Self