We report an orientation-sensitive omnidirectional vibration sensor based on fiber Bragg gratings (FBGs) inscribed in a seven-core optical fiber. By monitoring the central wavelength shifts of three FBGs in the central core and two outer cores, orientation information in 0-180° range as well as the acceleration value are obtained. The performance of the vibration sensor is characterized at different frequencies, orientations and accelerations. Comparison results for orientation discrimination using different groups of outer cores are investigated to enhance the reliability of the vibration sensor. The experimental results demonstrate an accuracy as high as 0.01° for orientation discrimination. The compact size and simple structure make the vibration sensor potentially superior in industrial applications where precise monitoring of the orientation is a necessity.