Mosques in Islamic culture, not only represent a place of worship, but also a place for solving and clarifying everyday disagreements. It is also a place where many various ceremonies take place and has always been in the center of attention and respect; therefore, in an artistic and industrial point of view, the fortifications and strength of the mosques, also the glamour and grace create an exceptional and intellectual site. In other words, mosque is a general place where all the arts and masterpieces come together. The decorations of the mosques have always been an important factor, since it was the center of the manifestation of Islamic art. One of the fundaments in Islamic decorations is the usage of religious and philosophical symbolism embedded within geometrical patterns, which influences the spirit of the worshiper and helps to improve the sense of divinity and unity. Additionally, the spiral patterns with repetition of the related motifs create peace and harmony. Inscriptions also have an important role in architecture; they display the beauty and unity of words and patterns. The masters of Calligraphy and inscriptions arrange the words and patterns in a masterly way to emphasize on the words of God and Islamic prayers; furthermore inscriptions can be divided into 3 groups: Quranic, Prayers and Hadith. This essay will study on the Inscriptions and decorative elements in Islamic architecture existing in mosques, and also the procedure of these elements in modern mosques, that are based on modernized architectural techniques. Modem mosques do not fully convey the spiritual and intellectual values and its existence as a divine and holy place is gradually weakened; moreover, its importance is equal to its cultural and political aspects. As a result, modem mosques have been distorted in many ways, including its traditional and architectural manners, such as its dome, minaret and mihrab; also the use of decorative arts has also been altered.