Berndt Johan Aminoff was born in Narva on the 16th of March 1697. During the Great Northern War, when the Russians attacked Ingria, both his mother Elisabeth von Konow and his siblings joined the rest of the family's women and children on their escape from the area. Berndt Johan remained in Narva, most likely in the care of his uncle, Adolf Berndt von Konow. Von Konow was however captured and possibly killed by the Russians during an counterattack made from Narva on the 9th of June 1704.  After Narva fell to the Russians on the 10th of August 1704, Berndt Johan was captured and sent to Moscow. He was only seven years old at the time. In Moscow he was taken into the care of Prince Repnin, rebaptized in the Greek Catholic (orthodox) Church, and raised amongst the sons of the prince. I Moscow Berndt Johan got in touch with his father, Gregori Aminoff, who had been captured at Perevolochna in 1709. He made sure that his son secretly received education in the Lutherian faith.  

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Berndt Johan began his career in the Russian army in 1711, when he as a page followed czar Peter (later known as Peter the Great) to the river of Pruth and the city of Husi, where the Russian had been surrounded by the Turkish. The peace treaty of the Russo-Ottoman war of 1710-1711 (also known as the Pruth River Campaign) was signed later the same year. Two years later, in 1713, Berndt Johan followed the Russian army to Pomerania, this time as an adjutant. In the year of 1717 he followed the Russian army to Hungary, where he was injured twice. The first time by an arrow, the second time in a combat with a Turkish officer, who didn't survive their combatte. On his way back to Russia, Berndt Johan decided to take a detour via Denmark, where he joined the Danish Life Guards, until he was forced to flee from a duel. He arrived in Riga in 1718. Thanks to a recommendation by the same prince Repnin who raised him in Moscow, he was promoted  lieutenant shortly after his arrival.  

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The treaty of Nystad ended the war between Russia and Sweden in September 1721. Unlike most of the Swedish prisoners of war, Berndt Johan wasn't allowed to return to Sweden, since he had been naturalised a Russian subject. In 1723 he did however abscond for the second time, travelling through Poland and Prussia first to Stralsund, and then to Stockholm, where he disaffiliated himself from the Greek Catholic Church. On the 18th of May 1725 Berndt Johan was given the rank of feldwebel of Nylands infanteriregemente (the Nyland Regiment of Foot)  and the company of Karis. He also received a residence in Pohja, where he lived until 11 Aug 1735, when he was dismissed with the rank of lieutenant.  

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In 1743, during the "Lesser Wrath" (1742-1743), when Finland was under Russian occupation, Berndt Johan participated in a revolt plan led by his younger brother Carl Gustaf Aminoff and K.M. von Numers. These plans were however abandoned since the peace negotiations between Sweden and Russia already had led to positive results in June 1743. The peace treaty was signed the same year in early August.  

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Berndt Johan married Christina Catharina Körning in either 1725 or 1726. She died in 1736 at Rilax. She had inherited the manor of Rilax from her father in 1726. Berndt Johan, who had taken care of the manor since 1730, gave up all his claims in favor of their son Fredrik, after the death of Christina Catharina. In 1737 Berndt Johan married his second wife, Anna Elisabeth Giös. 

 

Berndt Johan died on the 26th of March 1779, 82 years old, at Gammelby in Kimito Parish, one of the estates he had owned during his lifetime.