This note addresses a leader-follower consensus control problem for second-order multi-agent systems in a complicated scenario where the agent states are partially measurable and the agent dynamics are intrinsically nonlinear. More specifically, when the states of an agent are not fully measurable, a measurement output is thus defined. As a typical example, the measurement output is defined as the position of an agent while its velocity is unmeasurable. We propose a measurement output feedback controller with a dynamic observer for the unmeasurable states. Moreover, the proposed controller with sufficiently large but explicitly designed gains is able to deal with system nonlinearities when the region of attraction is semi-globally specified.