Jenkins played in the Jenkins Orphanage Band when young, and attended Wilberforce University. following this he played with Edgar Hayes and Horace Henderson (1924–28) before taking a position in Duke Ellington's Orchestra in 1928. As a member, he soloed in the 1930 film Check and Double Check during a performance of the song "Old Man Blues". He remained with the Ellington Orchestra until 1935, when lung problems forced him to quit.
He recovered and formed his own group in 1935, recording one session as a leader; sidemen included Ward Pinkett, Albert Nicholas and Bernard Addison. After this he played with Luis Russell in 1936. In 1937-38 he played with Ellington again, and for a short time thereafter played with Hayes Alvis. After 1938, his lung ailment returned and he retired from performance. In later years he worked in songwriting, disc jockeying, and in music press, and became a deputy sheriff in Fort Worth. Stanley Dance, writing about a concert played by Ellington and Sarah Vaughan: "There was a good crowd in the huge auditorium that night...The promoter, we were told, had a problem because of ticket counterfeiting. Deputy Sheriff Freddy Jenkins came in dressed Texas style with a big hat on his head and gun on hip. He looked a picture of health as he made an onstage speech and presentation to his former employer."