The article is devoted to the Russian-Prussian political relationships in the second quarter of the 19th century. The ties between the Russian and Prussian courts had historically been very close since the era of Peter the Great as well as were those between the Romanovs and the Hohenzollerns during the reign of Nicholas I. In the course of the latter, Russia and Prussia were bounded by allied relations within the framework of the Holy Alliance that existed since 1815. Having joined the circle of "great powers" due to its weapons and sizable army, Prussia at the same time was the weakest of the "great". Prussia was closely bound up with Austria and Russia due to the ties of commitment to the principles of the Holy Alliance and the monarchical solidarity of the ruling sovereigns. Not being an active player on the European arena, Prussia basically followed the path of political initiatives of the Russian Empire. After the end of the Russian-Turkish war of 1828-1829, Prussia was known as a devoted friend of St.-Petersburg. Prussia managed to maintain benevolent neutrality even in the light of the full-scale protest of the European against Russian military initiatives. Among the “northern” courts, that established the “threefold” concord, - Russia, Austria and Prussia - the latter was the weakest link in a fairly stable union of the three monarchies. Prussia preferred to conduct its foreign policy relying on the Russian court, that allowed it to be less dependent on Austria, with which Prussia competed within the German Confederation. However, this did not mean that the Prussian government lacked its plans and preferences in international politics, which clearly manifested itself in the 1840s and led to the complete isolation of Russia in the beginning of the Crimean War.