The　hydrogen　evolution　reaction　(HER)　in　renewable　energy　systems　has　long　been　a　fascinating　process,　but　designing　highly　efficient　and　ultrastable　electrocatalysts　is　challenging.　Transition　metal-based　heterostructure　nanohybrids　are　currently　drawing　more　interest　in　the　field　of　electrolysis　because　nanohybids　can　optimize　kinetic　processes　while　simultaneously　lowering　charge　transfer　resistance　and　increasing　the　electrochemically　active　electrode＇s　surface　area　at　the　reaction　interface.　Here,　we　propose　a　concept　for　a　two-step　colloidal　hot　injection　electrocatalyst　based　on　NiSe/ReSe2　nanocomposites　that　is　extremely　effective　for　hydrogen　evolution　under　acidic　conditions.　The　as-obtained　nanocomposite　material　worked　efficiently,　attaining　a　current　density　of　10　mA　cm(-2)　at　a　substantially　lower　over-potential　of　120　mV　vs　RHE　as　compared　to　each　of　the　individual　components　i.e.　NiSe　nanoparticles　and　ReSe2　nanosheets.　As　single　component　catalysts,　ReSe2　nanosheets　and　NiSe　nanoparticles,　however,　achieved　current　densities　of　10　mA　cm(-2)　at　higher　overpotentials　of　172　mV　and　221　mV,　respectively.　Even　more　intriguingly,　the　NiS/ReSe2　nanocomposite　is　believed　to　give　a　faster　kinetic　process　for　HER,　as　evidenced　by　a　Tafel　slope　of　115　mV　dec(-1),　which　certainly　is　lower　than　that　of　the　179　mV　dec(-1)　and　190　mV　dec(-1)　for　pure　NiSe　and　ReSe2,　respectively.　NiSe　nanocrystallites　and　ReSe2　nanosheets　were　assumed　to　be　working　in　a　synergistic　manner　to　generate　the　electronic　structural　modification　that　led　to　the　noticeably　increased　electrocatalytic　properties.　In　order　to　make　highly　tuned　electrocatalysts　in　solids,　we　anticipate　that　the　fabrication　of　hybrid　structures　will　be　a　successful　strategy.　(C)　2022　The　Electrochemical　Society　(＂ECS＂).　Published　on　behalf　of　ECS　by　IOP　Publishing　Limited.