Receiving his commission as lieutenant on 31 May 1860, he served aboard the steam sloop in 1861, and on the steam sloop of the West Gulf Blockading Squadron in 1862–1863, participating in the capture of New Orleans, Louisiana, late in April 1862; seeing action in the bombardment and passage of Forts Jackson and St. Philip, at the Chalmetto batteries, and in the destruction of rebel flotilla and transports on 24 April 1862, and in the passage of the Vicksburg batteries in June. He was present when the Confederate ram made an attack on the Union Fleet on 15 July 1862, receiving his commission as lieutenant commander the next day. Sicard commanded the during the two assaults on Fort Fisher in December 1864 and January 1865, and saw further action at the bombardment of Fort Anderson on 11 February 1865. Sicard then served aboard the steam sloop on the South Atlantic Blockading Squadron until the war's end.