Martensdale is a city in Warren County, Iowa, United States.

[4] According to the United States Census Bureau, the city has a total area of 0.40 square miles (1.04 km2), all of it land.

There were 185 housing units at an average density of 486.9 per square mile (188.0/km2).

Hispanic or Latino persons of any race comprised 1.4% of the population.

There were 198 housing units at an average density of 495.0 per square mile (191.1/km2).

30.6% of all households were made up of individuals, and 12.9% had someone living alone who was 65 years of age or older.

There were 181 housing units at an average density of 479.2 per square mile (185.0/km2).

23.0% of all households were made up of individuals, and 8.0% had someone living alone who was 65 years of age or older.