In 1927, Reddick became an instructor in journalism at the University of Texas's school of business administration, while also writing as a part-time correspondent for The Christian Science Monitor. He would remain at the university, in various positions, for the rest of his career. The following year, Reddick joined the University Presbyterian Church in Austin and earned a master's degree in government from UT. In 1934, he married Marjorie Bryan of Cleburne, Texas, a schoolteacher and fellow UT graduate. They would go on to have two children and would remain married until his death.
A vote among UT students named Reddick the school's most popular professor in 1935. In 1938, he wrote "Journalism and the School Paper," a journalism guide for student writers. That same year, he took a leave of absence to earn a Ph.D. in journalism from the University of Missouri, which he received the following year. Reddick was one of the first five men in the country to earn the degree. His research there included examining American journalism during the First World War, a timely subject given the outbreak of the Second World War that year. Reddick's dissertation, "The Newspaper as a Recorder of Contemporary History: A Case Study of the Reporting of the French Occupation of the Ruhr in Three American Newspapers," was completed in 1940. Shortly after returning to Austin, Reddick received another leave of absence to teach at Columbia University, where he taught feature writing and a new "orientation" course in journalism.
Reddick returned to Austin in 1942. For the next thirty-two years, he taught at UT, where his students included many notable future journalists. Among them were Walter Cronkite, Bill Moyers, Liz Carpenter, Ben Sargent, Karen Elliott House, Staley T. McBrayer, and Lady Bird Johnson. Moyers later credited Reddick for having "stoked my passion for journalism". In 1949, Reddick wrote "Modern Feature Writing," which the journal College English called "a practical and thorough introduction to the writing of feature articles for both magazines and newspapers by a teacher of long experience." Reddick founded Texas Presbyterian, the monthly magazine of the Texas synod of the Presbyterian Church, in 1953, and served as an advisor and contributor to the publication.
In 1956, he was named associate dean of the college of arts and sciences. Three years later, Reddick was picked to succeed Paul J. Thompson as director of the School of Journalism. He served in that position until 1965, when the School of Journalism was merged with the Department of Speech, and the Department of Radio-Television-Film to create a new School of Communications. Reddick was appointed as the new school's first dean. He said that in establishing the combined program, "we are encouraging greater cooperative efforts and more common enterprises."
Reddick retired as dean of the School of Communications in 1969, as UT required deans to retire at 65. In public remarks that year, Cronkite said that Reddick had "brought the business [of journalism] to a profession" and "created proof that good teachers and good schools of communication can do a good job of producing good journeymen newspapermen."[28] After retiring as dean, he took a leave of absence from UT to serve for a year as the first dean of the University of Tennessee's new college of communications. After the 1969–70 academic year, Reddick returned to UT as a professor of journalism. In 1974, the College of Communication established the DeWitt Carter Reddick Award in his honor, recognizing "excellence in the field of communication." Cronkite was the first recipient, with Lady Bird Johnson in attendance.
He retired that year, but taught one course the following year as professor emeritus and remained active as a consultant, writer, and speaker. On August 22, 1980, Reddick died at his home at the age of 76. After his death, Liz Carpenter said of Reddick that "[w]ith his magical mix of learning and humor, he took us all — so young and green and ignorant — and made us want to be reporters. Everything he touched turned to life, and he touched thousands."
