Single-walled carbon nanotubes (SWCNTs) have attracted intense interest in recent years due to their suitability for a wide range of applications, such as nano-sensors and nano-actuators. The primary objective of this paper is presenting a simplified nonlocal finite element model to investigate the potential application of CNTs as a nanomechanical mass sensor. Nonlocal differential elasticity of Eringen is exploited to reveal the long-range interactions between atoms. The CNT resonator is proposed as a bridge Euler-Bernoulli nanobeam with attached mass. An efficient finite element model is developed to discretize the nanobeam domain and solve the equation of motion numerically. The effect of nonlocal parameter on vibration characteristics is discussed and compared with published works. The effects of added mass on the nonlocal frequency shift percentage and higher vibrational modes are discussed in details. Numerical results show that the mass sensitivity of the nanotube sensor is in the zeptogram range.