A dual purpose cycle includes a frame unit, a wheel unit, a hub unit, and two crank arm units. The wheel unit includes a front wheel rotatably mounted to the frame unit. The hub unit surrounds an axis, extends though the front wheel, and includes opposite mounting portions respectively disposed at two opposite sides of the front wheel. Each of the mounting portions has an end surface facing oppositely of the front wheel, and an engaging groove indented from the end surface along the axis and having a non-circular cross-section. Each of the crank arm units includes an engaging member having a non-circular cross section, and removably and engagingly inserted into the engaging groove of a respective one of the mounting portions.