Rabbi Mordechai ben Avraham Yaffe, known as the Levush or the Baal HaLevushim after his work, was born around 5290 (1530) in Prague, into a family that traced its descent from Rashi. His father, Rabbi Avraham Yaffe, a pupil of Rabbi Avraham ben Avigdor, became rabbi of all Bohemia. He studied Torah in Lublin and Cracow under Rabbi Shlomo Luria, the Maharshal, and Rabbi Moshe Isserles, the Rema. After his marriage he returned to Prague and founded a yeshiva there, but in 1561 the Jews were expelled from Prague and all of Bohemia, and he left for Italy.

He lived for more than ten years in Italy, in Mantua and Venice, where he perfected himself in mathematics, astronomy, philosophy and other sciences. According to tradition it was during those years that he studied Kabbalah with Rabbi Matityahu Delacrut, author of Tzel HaOlam, in whose house he lived; his Kabbalah followed the pre-Lurianic Sephardic school. Between 1572 and 1578 he returned to Poland and was appointed rabbi of Grodno, where he built a splendid synagogue; following a dispute he moved in 1588 to Lublin, where he became one of the leaders of the Council of Four Lands, and in 1590 to Kremenetz. When the Maharal left the rabbinate of Prague in 1592, he took his place, and when the Maharal returned in 1599 he was appointed rabbi of Posen, where he served until his death. He attended the fairs of Jaroslaw and Lublin, where the leaders of the large communities met.

His books display vast learning: he dealt with biblical exegesis, halachah, homiletics, philosophy, the sciences and Kabbalah. He took a positive view of the study of secular wisdom and firmly disagreed on this point with his teacher the Maharshal, who regarded it as a waste of Torah study. Among his students were Rabbi Yissachar Ber Eilenburg, author of Beer Sheva, and Rabbi Yaakov Koppelman, author of Ohel Yaakov on the Sefer HaIkkarim.

He is famous for his monumental series the Levushim, or Levush Malchut, ten books whose titles are taken from the verse in Esther, "And Mordechai went out from the presence of the king in royal apparel...": Levush HaTechelet and Levush HaChur on Orach Chaim, Levush Ateret Zahav on Yoreh Deah, Levush HaButz VeHaArgaman on Even HaEzer, Levush Ir Shushan on Choshen Mishpat, Levush HaOrah on Rashi's commentary and the Mizrachi, Levush Simchah VeSasson (sermons, the only one never printed), Levush Pinat Yikrat on the Guide for the Perplexed, Levush Eder HaYakar on Maimonides' laws of sanctifying the month and on Avraham bar Chiya's Tzurat HaAretz, and Levushei Or Yekarot on the kabbalistic commentary of Rabbi Menachem Recanati. In his introduction, which opens with the words "Thus says the tailor," he explains that he had first intended to compose a work covering all the laws of the Tur and Beit Yosef, but that the appearance of the Shulchan Aruch, and then of the Rema's glosses on Ashkenazi customs, led him to write a book that sets out the roots and reasons of the laws ruled in the Shulchan Aruch, midway between the lengthy Beit Yosef and the overly concise Shulchan Aruch. He worked on it for almost fifty years. The Levush was for many years a popular code among Ashkenazi Jews and remains a basic reference for halachic authorities; Rabbi Eliyahu Spira of Prague wrote the commentaries Eliyah Rabbah and Eliyah Zuta on it.

He passed away in Posen on 3 Adar II 5372 (March 1612).