In this paper, we report for the first time that in an islanded microgrid comprising a number of grid-forming converters, several hidden attractors may exist, including periodic orbits, quasi-periodic orbits, and chaotic attractors. The system operating at a stable equilibrium point may be brought to one of these hidden attractors under some transient disturbance. Then, the system will exhibit sustained oscillation, and the grid-forming converters will cease to synchronize. Full-circuit cycle-by-cycle simulations are provided to verify these findings.