In the ninth century AH, the patronage of Timurid rulers contributed to the flourishing of the arts of the book. During this period, the Shiraz ketābkhāna (royal manuscript workshop), under the patronage of Ebrāhīm Solṭān, continued the traditions of manuscript production established in the preceding period. In contrast, the Herat ketābkhāna, under Bāysonqor Mīrzā, developed a distinct approach through the incorporation of various artistic traditions. Illumination is also one of these decorations. The present study aims to identify the stylistic characteristics of manuscript illumination in these two ketābkhāna and to compare them to determine their stylistic similarities and differences. Eight illuminated manuscripts form the corpus of this study. The illumination of the groups of manuscripts was analyzed and compared in terms of the placement and composition of illuminated decoration, framing arrangements, types of motifs, the frames, and the colors employed. The findings indicate that the two groups of manuscripts are broadly similar in terms of the placement of illuminated decoration; however, the Shiraz manuscripts generally contain more extensive illuminated areas. In relation to the frames, the motifs in the Shiraz manuscripts are finer and more densely arranged, whereas those in the Herat manuscripts display greater detail. Khata’i motifs are predominant in the Shiraz manuscripts, while arabesque motifs occur more frequently in the Herat examples. In the Shiraz manuscripts, illuminated framing arrangements more commonly feature central medallions and flanking medallions, whereas circular geometric designs are more characteristic of the Herat manuscripts