Conrad had fought as an ally of Isaac II Angelus of Byzantium, and was married to Isaac's daughter Theodora. However, the Greeks were suspicious of him as a Westerner, and he fled to Syria in 1187. He arrived at Tyre soon after the fall of Jerusalem, and took responsibility for its defense when Saladin besieged it. He defeating the Egyptians in a sea battle and successfully withstood the siege.
Due to his victories he no longer recognized Guy of Lusignan as king of Jerusalem, and forced him to leave Tyre; Guy then joined the Crusaders to conquer Acre. When Guy's wife Sibylla died during the siege of Acre, Guy technically no longer had a claim to the throne. Conrad then married Sibylla's sister Isabella, even though he was still married to Theodora. As Guy was a vassal of Richard I of England, Richard supported him in this political struggle, while Conrad was supported by Philip II of France and Leopold of Austria[?].
After the capture of Acre, Guy was confirmed as king, and Conrad was made his heir. However, in April of 1192, under pressure from the English barons, Guy was given (or, more accurately, was forced to purchase) the kingship of Cyprus, while Conrad was named king of Jerusalem. Conrad's rule did not last long. On April 28, Isabella was late in preparing dinner for him, so he went to eat at the house of the Bishop of Beauvais. The bishop had already eaten, so Conrad returned home; on his way he was stabbed to death by two Assassins. Many felt Richard was responsible for the assassination, though this is unlikely, or at least impossible to prove.
Conrad's brother Boniface of Montferrat was the leader of the Fourth Crusade; their brother Rainier was a son-in-law of Manuel Comnenus, and another brother, William[?], was the father of Baldwin V of Jerusalem.