Like all post-E8 British E-class submarines, E23 had a displacement of at the surface and while submerged. She had a length of and a beam of .[2] She was powered by two Vickers eight-cylinder two-stroke diesel engines and two electric motors.[3] [4] The submarine had a maximum surface speed of and a submerged speed of . British E-class submarines had a fuel capacity of of diesel and ranges of when travelling at .[2] E23 was capable of operating submerged for five hours when travelling at .
E23 was armed with a 12-pounder QF gun, mounted forward of the conning tower. She had five 18-inch (450 mm) torpedo tubes, two in the bow, one either side amidships and one in the stern with ten torpedoes on board.[3]
E-class submarines had wireless systems with power ratings; in some submarines, these were later upgraded to systems by removing a midship torpedo tube. Their maximum design depth was although in service some reached depths of below . Some submarines contained Fessenden oscillator systems.[2]
Her complement was three officers and 28 men.[2]