In the Seven Years' War, his brilliant conduct at the churchyard of Leuthen and at Hochkirch won him promotion to major.
In 1760, in the almost lost Battle of Torgau, Möllendorf was captured by the Austrians, but released in 1761, and was made major general later in the year.
At the Battle of Burkersdorf Möllendorf commanded a brigade that participated in the successful assault of the fortified Austrian positions.
He lived the remainder of his life in retirement and on January 28, 1816, Wichard von Möllendorff died in Havelberg at the age of 92.
He found his final resting place in a mausoleum in the Gadow Castle Park (at Lanz, Brandenburg), built in 1816 according to plans by the architect Salomo Sachs.