Assam has a rich history of the Ahom dynasty for 600 years. With the first Ahom King Sukapha (A.D. 1228–1268) leadership, they set up their first capital in the Charaideu district of Assam. As for which, most of the Ahom architectures are observed in and nearby Sivasagar and Charaideu area of Assam. Most of the Ahom monuments are preserved under the Archaeological Survey of India (ASI), Assam and Directorate of Archaeology, Guwahati, Assam. These monuments were constructed using mostly bricks, stones and mortar. Noticeably, the ornamentations in the brick monuments have managed to survive in fragments and sections; this is due to the effect of natural causes and the climatic condition of the environment. In some cases, the restoration process reduces the ancient aesthetic due to lack of understanding of the underlying design principles of ornamentation. Most historians and scholars have studied the iconography and archaeological findings of these monuments; the study on Ahom architectural ornamentation is significantly less. A pilot study was conducted to identify the surviving ornamentation in brick architecture monuments. Based on the identification, a categorization theory has been adopted to segregate the data. The categorization is based on the architectural sections of monuments that primarily includes motifs and pattern types. This paper identifies and compares the visual elements of ornamentation using formal analysis. It discusses the underlying design principles of ornamentation. The results and analysis of this paper provide a significant contribution to the conservation of traditional art and early architectural ornamentations. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.