Conrad went on to rule in the newly acquired Neumark part of Brandenburg east of the Oder River, though he rarely appeared on the political scene. On one occasion, he assisted his brother Otto IV, when they allied with Duke Mestwin II of Pomerelia according to the 1269 Treaty of Arnswalde, occupying the Pomerelian city of Gdańsk and gaining the Pomeranian territory around Rügenwalde.
He died in 1304 and was buried beside his wife in Chorin Abbey. There is an entry in the register at Chorin as follows:
Anno 1304 ist zu Sched (?) gestorben Markgraf Conrad (I.) Churfürst zu Brandenburg und ist allhier begraben.
Andreas Thiele: Erzählende genealogische Stammtafeln zur europäischen Geschichte. Deutsche Kaiser-, Königs-, Herzogs- und Grafenhäuser, vol I, part 1, table 223
^Theodor Fontane: Wanderungen durch die Mark Brandenburg, in: Jutta Neuendorff-Fürstenau (ed.): Theodor-Fontane-Gesamtausgabe, part 2, Hanser Verlag, 1987, p. 91