This study investigates the use of Ni(OH)₂ nanocrystals grown on graphene sheets with varying degrees of oxidation as electrochemical pseudocapacitor materials. Single-crystalline Ni(OH)₂ hexagonal nanoplates directly grown on lightly-oxidized, electrically-conducting graphene sheets exhibit high specific capacitance (~1335 F/g at 2.8 A/g and ~953 F/g at 45.7 A/g) and excellent cycling stability. The high specific capacitance and rate capability make these materials promising for supercapacitors with high energy and power densities. The simple physical mixture of pre-synthesized Ni(OH)₂ nanoplates and graphene sheets shows lower specific capacitance, highlighting the importance of direct growth on graphene for efficient charge transport. Ni(OH)₂ nanoplates grown on heavily-oxidized, electrically-insulating graphite oxide (GO) perform significantly worse, emphasizing the role of graphene quality and nanomaterial morphology and crystallinity in the electrochemical performance. The results underscore the importance of rational design and synthesis of graphene-based nanocomposite materials for high-performance energy applications.This study investigates the use of Ni(OH)₂ nanocrystals grown on graphene sheets with varying degrees of oxidation as electrochemical pseudocapacitor materials. Single-crystalline Ni(OH)₂ hexagonal nanoplates directly grown on lightly-oxidized, electrically-conducting graphene sheets exhibit high specific capacitance (~1335 F/g at 2.8 A/g and ~953 F/g at 45.7 A/g) and excellent cycling stability. The high specific capacitance and rate capability make these materials promising for supercapacitors with high energy and power densities. The simple physical mixture of pre-synthesized Ni(OH)₂ nanoplates and graphene sheets shows lower specific capacitance, highlighting the importance of direct growth on graphene for efficient charge transport. Ni(OH)₂ nanoplates grown on heavily-oxidized, electrically-insulating graphite oxide (GO) perform significantly worse, emphasizing the role of graphene quality and nanomaterial morphology and crystallinity in the electrochemical performance. The results underscore the importance of rational design and synthesis of graphene-based nanocomposite materials for high-performance energy applications.