Engelbert was elected Archbishop of Cologne as Engelbert I on 29 February 1216 and was consecrated on 24 September 1217, in which office he remained until his violent death. Engelbert came to enjoy the trust of Frederick II, Holy Roman Emperor, becoming imperial administrator in 1220 and guardian of the Emperor's son Henry. In 1222, Engelbert crowned twelve-years-old Henry as King of the Romans in Aachen. Engelbert remained Henry's tutor and guardian until his death. It is not clear to what extent Engelbert was personally involved with the Confoederatio cum principibus ecclesiasticis, a treaty with the ecclesiastical princes, which Frederick signed on 26 April 1220, although as Administrator of the German Kingdom he must have had at least some input. Clearly, however, in the increased powers it gave to all ecclesiastical princes it was of benefit also to the archbishops of Cologne, and the establishment and development of the new powers was part of Engelbert's archiepiscopal strategy. When Engelbert succeeded, the rights and territories of the archdiocese were in bad order, following a long period of civil unrest in Germany. He engaged himself at once in a series of campaigns and strategies to win them back and safeguard them, principally against the Dukes of Limburg and their allies the County of Cleves. Engelbert in turn set up alliances with Brabant and Namur. Engelbert also defended his personal inheritance as Count of Berg against Duke Waleran III of Limburg. In 1218 Engelbert's elder brother Count Adolf VI of Berg died on the Fifth Crusade without a male heir. Waleran considered himself entitled to inherit the County of Berg because his son Henry was married to Irmgard of Berg, Adolf's only daughter. According to the Salic law, however, Engelbert was the heir. He won the dispute in two feuds. In 1220 a peace was concluded and Waleran's claim settled by the payment of a year's revenues. Engelbert granted town privileges to many places, including Wipperfürth, Attendorn, Brilon, Siegen, Werl and Herford, Vianden, Hamm, Neuerburg and Manderscheid. During his incumbency as archbishop, Engelbert continued to fight for the re-establishment and security of the Archdiocese of Cologne both as an ecclesiastical authority and also as a secular territory.. Not only did he constantly battle, by all means necessary, for the secular well-being of the lands of the archdiocese, of which he may be counted the de facto founder as a significant state; he also took energetic measures for the effective regulation of the City of Cologne itself; and he was a zealous champion of the religious throughout his archdiocese.
Death
Engelbert earned the respect and affection of his subjects through his devotion to justice and his energy in maintaining law, and took great pains to ensure the well-being of the religious within his authority. However, his effectiveness in achieving his goals by all means necessary, including military action, his allegiance to the pope and the emperor, and his uncompromising defence of the law and the rights of religious persons and bodies, brought him into conflict with the nobility, including his own family, and this led to his death. His cousin Count Frederick of Isenberg was vogt of Essen Abbey, and abused his position by defrauding the nuns. Engelbert was determined to protect the nuns' interests and sought to bring Frederick to justice. On 7 November 1225 while they travelled together to Cologne from a judicial hearing in Soest, Engelbert was killed, possibly by Frederick, in a defile near present-day Gevelsberg near Schwelm. It seems probable that a group of disaffected nobility was behind the attack which may have been intended to take Engelbert captive rather than kill him. Engelbert's body was taken to Cologne on a dung-cart, and when examined, found to have forty-seven wounds.
Veneration
Engelbert's body was buried in Cologne Cathedral on 24 February 1226 by order of CardinalConrad of Urach, the papal legate, who declared him a martyr, though a formal canonization did not take place. His remains are preserved today in a Baroque shrine prepared on the authority of Ferdinand of Bavaria, archbishop of Cologne, who in 1618 also ordered the celebration of his feast on 7 November.