The influence of C ₆ H ₁₆ N ₂ addition on the microstructural and superconducting properties of MgB ₂ was systematically investigated. Unlike previously reported carbon sources, the C ₆ H ₁₆ N ₂ additive had no effect on the lattice parameters of MgB ₂ . However, the obvious improvement of critical current density ( J _c ) was obtained for C ₆ H ₁₆ N ₂ added MgB ₂ without carbon substitution for boron. The average grain size was reduced with the addition of C ₆ H ₁₆ N ₂ . Additionally, different numbers of spherical MgB ₂ grains appeared inside the C ₆ H ₁₆ N ₂ added MgB ₂ . As the added amount of C ₆ H ₁₆ N ₂ increased, the active cross-sectional area fraction ( A _F ) values first increased then decreased. The possible reasons for these results have been discussed. The additive C ₆ H ₁₆ N ₂ resulted in a small depression in T _c and slightly increased the Δ T _c of MgB ₂ at 0 T. The H _c2 (T) and H _irr (T) values of C ₆ H ₁₆ N ₂ added MgB ₂ samples are larger than those of pure MgB ₂ at temperatures below 25 K. It was concluded that the reduced grain size and the improved grain connectivity were mainly correlated with the enhancement of the J _c , F _p , H _c2 , and H _irr performances in C ₆ H ₁₆ N ₂ added MgB ₂ superconductors.