Tidwell was the son of Robert and Nannie Graves Tidwell of Blount County. He completed the course at the Central Alabama Agricultural School in Blountsville in 1901 and was appointed principal of the two-room Collins Chapel School near Thorsby.
He left in 1903 to enroll at the University of Alabama, and he played on the 1904 Alabama Crimson Tide football team before completing his bachelor of science in 1905. In 1910 he was hired as principal of Ensley High School, then in the independent City of Ensley. He left in 1913 to become superintendent of the Tennessee Coal, Iron and Railroad Company's educational department, overseeing schools for employees' children at company towns in Jefferson, Bibb and Blount Counties.
In 1917 Tidwell was made Assistant State Superintendent of Education, and took over the Alabama Department of Education as Superintendent in 1927. Two years later he resigned to enroll in graduate studies at Columbia University in New York.
Tidwell was appointed dean of extension services at his alma mater in 1930 and retired in 1954 after helping to establish the first organized network of extension centers in Birmingham and Huntsville that eventually became full universities under the University of Alabama System and, independently in Mobile as the University of South Alabama. His efforts were also instrumental in the early development of Alabama Public Television.
In retirement, Tidwell continued to serve as an assistant to the President of Stillman College. He also spent a year in Iraq as a U.S. State Department consultant to that country's ministry of education. He was also a deacon of First Baptist Church of Tuscaloosa.
In 1956, Tidwell Hall in Birmingham, was named in his honor, but the name did not appear on the outside of the building until the late 1960s. Tidwell was survived by his wife, Bessye. He was buried at Memory Hill Gardens in Tuscaloosa.
- McCollum, Marvin Gardner Jr (1962) Robert Earl Tidwell and Public Education in Alabama. Tuscaloosa: University of Alabama College of Education
- "Dr Robert Tidwell" obituary (January 19, 1977) Tuscaloosa News