High energy extraction efficiency of 48±4% for the cavity mode cross section (17.5%±1% for the entire lasant cross section) and high energy gain of 71±1 dB have been demonstrated simultaneously, for the first time, in a laser‐diode pumped Nd:YAG regenerative amplifier (RA). The RA was operated at an initial small‐signal gain of 3.15±0.20, an input pulse energy of 0.5±0.1 nJ (pulse width of 910±12 ps), an amplified output pulse energy of 6.0±0.3 mJ (pulse width <1 ns), and a repetition rate of 50 Hz. The dependence of energy extraction efficiency on initial small‐signal gain of the RA was shown to be well fitted with the theory of Lowdermilk and Murray [J. Appl. Phys. 51, 2436 (1980)].