In 1866 the Grand Duchy joined the North German Confederation and the Zollverein, and began to pass more and more under the influence of Kingdom of Prussia, who in the Austro-Prussian War with Empire of Austria had been aided by the soldiers of Mecklenburg-Strelitz. In the Franco-Prussian War also Kingdom of Prussia received valuable assistance from Mecklenburg-Strelitz. In 1871 the grand duchy became a state of the German Empire. There was now a renewal of the agitation for a more democratic constitution, and the German Reichstag gave some countenance to this movement. In 1904 Adolphus Frederick V, a son of the grand duke Frederick William and his wife Princess Augusta of Cambridge, daughter of Prince Adolphus, became grand duke of Mecklenburg-Strelitz. In 1907, the Grand Duke promised a constitution to their subjects. The duchy had always been under a government of feudal character, the grand duke having the executive entirely in their hands (though acting through ministers), while the duchy shared a diet (Landtag), meeting for a short session each year, and at other times represented by a committee, and consisting of the proprietors of knights' estates (Rittergiiter), known as the Ritter-schaft, and the Landschaft or burgomasters of certain towns. Mecklenburg-Strelitz returned one member to the Reichstag. The grand duke still styled Prince of the Wends.

The lingering end of the ruling family of Mecklenburg-Strelitz occurred just prior to the loss of actual monarchy in developments of World War I - at that time, there existed only two surviving recognized male dynasts of Strelitz, the young Grand Duke Adolphus Frederick VI and his cousin Charles Michael who was in Russian service, being a son of Grand Duchess Catherine Mikhailovna. In 1914, before the proclamation of war between Germany and Russia, Duke Charles Michael renounced his Mecklenburgish citizenship. On 23 February 1918, Grand Duke Adolf Frederick VI committed suicide, leaving his cousin Charles Michael as heir to the Strelitz throne. Being in Russia, however, Charles Michael did not assume the throne and in 1918, he wrote to Grand Duke Frederick Francis IV of Mecklenburg-Schwerin, who was acting as regent in Strelitz, stating that he wished to renounce his rights of succession to Strelitz, though the letter was only received by Frederick Francis in 1919 after the end of German monarchies, so the issue of succession could not be resolved in time.

The House of Mecklenburg-Strelitz survives to this day descending from Duke George, the morganatic son of Duke George Alexander with Countess Natalia Carlow and nephew of Duke Charles Michael, who adopted him in 1928. George subsequently assumed the title "Duke of Mecklenburg" (Serene Highness) which was acknowledged by Grand Duke Frederick Francis IV of Mecklenburg-Schwerin. He was later given the style of Highness by the House of Mecklenburg-Schwerin. George's grandson Borwin is the present head of the House of Mecklenburg-Strelitz. The American county of Mecklenburg which includes the city of Charlotte, North Carolina is named after the duchy.

List of the Dukes and Grand  Dukes of Mecklenburg-Strelitz

	Name (lived)	Reign	Notes
	Adolf Frederick II (19 October 1658-12 May 1708)	1701-1708	(Uncle of Frederick William of Mecklenburg-Schwerin) Duchy created, inaugural Duke
	Adolf Friedrich III (7 June 1686-11 December 1752)	1708-1752	(Son of Adolf Frederick II)
	Adolf Friedrich IV (5 May 1738-2 June 1794)	1752/53-1794	(Nephew of Adolf Friedrich III)
	Charles II (10 October 1741-6 November 1816)	1794-1816	(Brother of Adolf Friedrich IV) from 1815 Grand Duke
	Georg (12 August 1779-6 September 1860)	1816-1860	(Son of Charles II)
	Friedrich Wilhelm (17 October 1819-30 May 1904)	1860-1904	(Son of Georg)
	Adolf Friedrich V (22 July 1848-11 June 1914)	1904-1914	[Son of Friedrich Wilhelm]
	Adolf Friedrich VI (17 July 1883-23 February 1918)	1914-1918	(Son of Adolf Friedrich V)
	Frederick Francis IV (9 April 1882-17 November 1945)	1918	District Administrator