Nikaia is located about 8 kilometres (5 miles) WSW of central Athens, and about 4 km (2 miles) N of downtown Piraeus. The main streets are Gregori Lambraki Street and Petrou Ralli Street.
The area was made up of farmlands. Mixed farming was common. Urban development replaced much of the farmlands between the 1930s and the 1950s. The area, like many others around Greece, owes its population eruption to Greek refugees who left the Asia Minor coast after the 1922 war ended. Today, most of the municipality is urbanized or residential. The area is made up of low hills.