This study presents five examples of Istanbul Art Nouveau residential architecture in Sarıyer and Beyoğlu districts and their current conservation state. The aim is to evaluate two family yalıs in Sarıyer and three apartment buildings in Beyoğlu. First, Art Nouveau characteristics, its emergence in Europe and Istanbul were investigated. It was important to understand the changes in residential architecture in late Ottoman Empire and see the differences between its late and classical examples before starting to examine the buildings. After the historical research, analysis work of the five case studies had been carried out in site scale including the near-by environment and in single building scales. The way followed was survey with conventional techniques, mapping for visual analysis; literature and archive research in the related municipalities and the conservation councils. Then, each building was evaluated with the information coming from the analysis work and finally a general evaluation became possible. In conclusion, it is observed that Sarıyer and Beyoğlu examples have different conservation problems. Sarıyer examples have conserved both their façade and plan characteristics. They are currently used with the same purpose as their original function, restored and maintained. Their conservation problems are mostly caused by the interventions through the years to their near-by environment their original building material was renewed. In Beyoğlu examples, it can be said that façade of the buildings were preserved but interior organization was changed due to the function changes in Beyoğlu in general. Facades have become shells of the modern interiors.