We report on high‐efficiency frequency doubling of a mode‐locked diode‐laser‐pumped Nd:YAG laser to 532 nm in a crystal of MgO:LiNbO3in an external enhancement ring cavity. At a pump power of 500 mW the mode‐locked Nd:YAG laser produced an average power of 66 mW incident on the enhancement cavity in pulses of 12 ps duration at a repetition rate of 366 MHz. This has been frequency doubled with a conversion efficiency of 53% to produce pulses at 532 nm of 35 mW average power in bandwidth‐limited pulses of 9.5 ps duration.