Records show that at least two lines of O'Higgins are armigerous.
In 1788 Don Ambrose O'Higgins, Marquis de Osorno of the Ballynary Line was confirmed with a coat of arms and crest by the Ulster King of Arms in Dublin. Records in the Genealogical Office in Dublin MS 165. p. 396-399 outline the pedigree of the Ballynary line and a Grant of Arms to Ambrose who was then a Brigadier General in the King of Spain's Army in Peru and Chile. The Arms that was granted to Ambrose is shown here:

An earlier Arms was recorded by Sir James Terry, Athlone Herald in the Court of James II at St. Germaine. King James was in excile in France and took his herald from Ireland with him where he continued to record and grant arms to the native Irish nobles including the O'Higgins of Monteige who originated in Kilmacteige in Sligo. This branch of the family moved to Limerick after they lost their lands and eventually relocated in Spain where one of them was knighted and became personal physican to the King of Spain. The arms granted to O'Higgins of Monteige are shown here:

While both of the above Arms relate to different branches of O'Higgins, they both contain a demi-griffin for the Crest on top of the shield.
Under the English laws of heraldry only the person to whom the Grant of Arms is made can use a Coat of Arms and after his death his heir. Other members of the family must apply to use a different version of the Coat of Arms. This is an approach currently held by the Chief Herald in Dublin. However, previous heralds took a different approach and accepted that some Coats of Arms existed from Gaelic times and as such all those who descended from the original family or sept could bear the arms of that sept. This was the view held by the first Chief Herald of Ireland Dr. Edward MacLysaght when he designated the first Arms above as a Sept Arms for all who descended from the O'Higgins of Ballynary. Whichever tradition is correct today it is advisable that individuals seek their own Grant of Arms within the appropriate jursidiction.
Although it is not a personal Arms, the City of Osorno in Chile has a Coat of Arms that relates to the O'Higgins family. In 1790s under the orders of Ambrosio O'Higgins, Osorno was rebuilt by Juan Mackenna, and declared officially re-populated in 1796 at the same time Ambrose was made Vice-roy of Peru. He was also awarded the title of Marquess of Osorno and had a special Coat of Arms created for the city. The Arms which is shown below is quartered with the Coats of Arms from the four lines of Ambrose's pedigree as follows clockwise O'Higgins, Brehan, O'Conor, and O'Fallon. In 1956 the City of Osorno issued a new decree confirming this Coat of Arms as it's offical symbol.
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(Heraldic graphics courtesy of Eddie Geoghan http://www.araltas.com/)