Electrocatalysis　plays　a　key　role　in　clean　energy　innovation.　In　order　to　design　more　efficient,　durable　and　selective　electrocatalysts,　a　thorough　understanding　of　the　unique　link　between　3D　structures　and　properties　is　essential　yet　challenging.　Advanced　3D　electron　tomography　offers　an　effective　approach　to　reveal　3D　structures　by　transmission　electron　microscopy.　This　mini-review　summarizes　recent　progress　on　revealing　3D　structures　of　electrocatalysts　using　3D　electron　tomography.　3D　electron　tomography　at　nanoscale　and　atomic　scale　are　discussed,　respectively,　where　morphology,　composition,　porous　structure,　surface　crystallography　and　atomic　distribution　can　be　revealed　and　correlated　to　the　performance　of　electrocatalysts.　(Quasi)　in-situ　3D　electron　tomography　is　further　discussed　with　particular　focus　on　its　impact　on　electrocatalysts＇　durability　investigation　and　post-treatment.　Finally,　perspectives　on　future　developments　of　3D　electron　tomography　for　eletrocatalysis　is　discussed.