A novel, compact diode-end-pumped conductively cooled Q-switched Nd:YLF laser is developed. A diode-end-pumped pair of Nd:YLF slabs and an intracavity-frequency-doubled configuration are adopted to increase conversion efficiency. Using 49.8-mJ incident pump pulse energy at 500-Hz repetition rate, the laser obtains 11-mJ pulse energy and 5.5-W average output power at 527-nm wavelength, achieving an optical–optical conversion efficiency of 22%. The pulsewidth is less than 15 ns, and the beam quality factors are M2x=1.28 and M2y=1.12.