The deep crustal structure of the Polatli-Nallihan-Karasu (NW Turkey) area was investigated by Magnetotelluric and Transient Electromagnetic measurements. All measurements were acquired as part of a national project called Crustal Structures of Turkey undertaken by the General Directorate of Mineral Research and Exploration of Turkey (MTA). Magnetotelluric data were collected from 44 stations located along a 250 km northwest to southeast profile crossing in succession the Istanbul Zone, Intra-Pontid Suture, Sakarya Continent, Izmir-Ankara Suture, Tavsanli Zone (the Tauride-Anatolide Belt), Intra-Pontid Suture and Sakarya Continent. After decompositional analysis and strike direction estimation, static shift is corrected by using transient electromagnetic data from MT apparent resistivity data. The processed MT data were inverted to derive a two-dimensional geoelectrical model. The estimated model is interpreted with the help of gravity data observed along the MT lines and using earthquake epicenter which occurred around MT measurement lines.