Aluminum-doped α-Ni(OH)2 microspheres with flowerlike hierarchical structure (H-Al-α-Ni(OH)2) were successfully synthesized via a facile hydrothermal method with the assistance of ionic liquid (1-butyl-3-methyl imidazolium tetrafluoroborate, [BMIM]BF4). The XRD pattern and elemental analysis confirm that aluminum species incorporates into the lattice of α-Ni(OH)2; SEM and TEM images reveal that the as-prepared microspheres are composed of numerous frizzy nanoflakes shell attaching vertically to the core. The resulting H-Al-α-Ni(OH)2 sample exhibits a specific surface area of 91.2m2/g and a mesopore distribution (2–20nm) based on the BET measurements. Furthermore, the hierarchical H-Al-α-Ni(OH)2 modified electrode displays a couple of well-defined reversible redox peaks (ΔE p =67mV and I a/I c =0.91) and a fast direct electron transfer rate constant (k s =3.32s−1), owing to the high dispersion of active species as well as abundant mass transfer channels which facilitate the mass/electron transfer. In addition, the modified electrode presents a significant electrocatalytic performance towards the oxidation of hydrazine with a linear response range (5.0×10−6–1.0×10−4 M), high sensitivity (144μA/μM cm2), low detection limit (0.8μM) as well as good stability. The hierarchical α-Ni(OH)2 with largely enhanced electrochemical behavior demonstrated in this work can be used in electrochemical sensor and electroanalysis.