ShieldPer fess Gules and Or, on a canton of the second a saltire Azure.
CrestThat for the regiments and separate battalions of the Pennsylvania Army National Guard: From a wreath of the colors Or and Gules, a lion rampant guardant Proper, holding in dexter paw a naked scimitar Argent hilted Or and in sinister an escutcheon Argent on a fess Sable three plates.
MottoFIRE FOR EFFECT.
ShieldThe service of the former organization, the 166th Field Artillery, is indicated by the divided shield which is red and yellow, representing the organization's assignment to the 22d Cavalry Division. The gold canton with the blue saltire thereon represents the unit's descent from Infantry through the two oldest units which were organized in 1858.
CrestThe crest is that of the Pennsylvania Army National Guard.
The coat of arms was originally approved for the 166th Field Artillery Regiment on 9 May 1940. It was redesignated for the 166th Field Artillery Battalion on 22 June 1954. It was redesignated for the 166th Artillery Regiment on 21 August 1961. The insignia was redesignated for the 166th Field Artillery Regiment on 21 July 1975. It was redesignated for the 166th Regiment with the blazon and symbolism revised on 28 May 1997.