Petachiah was born in Ratisbon (now Regensburg), Bavaria. He was the brother of Rabbi Yitzhak ha-Lavan ("the White") ben Yaakov, a renowned Jewish jurist. During his childhood he was probably tutored by such scholars as Judah the Pious (Yehuda ben Shmuel). He was the author of several glosses on the Talmud. As a young man he left Ratisbon, a city whose Jewish community was so renowned for its piety and learning that it was sometimes called the "Jewish Athens", and settled in Prague.
The date of his travels is uncertain. He probably set out from Prague sometime between 1170 and 1180, and was certainly in Jerusalem prior to 1187, since he describes it as being under the control of the Latin Kingdom of Jerusalem. As Judah the Pious is supposed to have written the surviving edition of Petachiah's travelogue, he must have returned to Ratisbon prior to that sage's death in 1217.
Petachiah traveled east from Bohemia, through Poland, Ruthenia, southern Russia (which he called Kedar), and the Crimea. He describes the remnants of the Khazars and the early Crimean Karaite community. He then went south through the Kipchak khanates and the Caucasus into Armenia, sojourning for a while in Nisibis. From there he travelled to Mesopotamia, visiting Nineveh, Sura, Pumbedita, and Baghdad before moving on to Persia. Turning westward, he journeyed up the Euphrates and into Syria, visiting Aleppo and Damascus. He travelled on to the Land of Israel, visiting holy sites in the Galilee and Judea, from whence he may have taken to the sea, because the next place he describes is Greece. From there, presumably, he returned home via the Balkans.
The date of Petachiah's death is unknown.